Mac
Abbreviation with 10 meanings
| Stands for | Macintosh |
|---|---|
| Meanings | 10 |
| Categories | Technology & Computing, Medical, Law & Legal |
| Also written | MAC |
Mac has ten meanings. The most common are Macintosh (computer) and Monitored anesthesia care (anesthesia); it can also stand for Media access control (address), Medicare Administrative Contractor, Minimum alveolar concentration, Mycobacterium avium complex and Material adverse change, plus 3 more listed below.
Meanings of Mac at a glance
| # | Mac stands for | Context |
|---|---|---|
| 1 | Macintosh | Technology & Computing › Computer |
| 2 | Monitored anesthesia care | Medical › Anesthesia |
| 3 | Media access control (address) | Technology & Computing › Networking |
| 4 | Medicare Administrative Contractor | Medical › Health Insurance |
| 5 | Minimum alveolar concentration | Medical › Anesthesia |
| 6 | Mycobacterium avium complex | Medical › Infectious Disease |
| 7 | Material adverse change | Law & Legal › Contract |
| 8 | Maximum allowable cost | Medical › Pharmacy |
| 9 | Mandatory access control | Technology & Computing › Cybersecurity |
| 10 | Message authentication code | Technology & Computing › Cybersecurity |
1. Macintosh
Technology & Computing · Computer Abbreviations · also used in medicine
Apple's line of personal computers running macOS, including the MacBook Air, MacBook Pro, iMac, Mac mini, Mac Studio and Mac Pro. Since 2020 Macs have used Apple-designed processors instead of Intel chips.
Example: Does the software run on a Mac, or is it Windows-only?
The original Macintosh went on sale on January 24, 1984, and was the first mass-market computer sold with a graphical interface and mouse as standard. Project founder Jef Raskin named it after the McIntosh apple, changing the spelling. Write "Mac" with only the M capitalized; all-caps MAC refers to a network MAC address or other terms.
2. Monitored anesthesia care (MAC)
Medical · Anesthesia Abbreviations
Anesthesia service in which an anesthesia professional monitors the patient and gives sedation and analgesia as needed during a procedure, while remaining ready to convert to general anesthesia. It is common for cataract surgery, endoscopy, minor orthopedic procedures and many outpatient cases.
Example: Colonoscopy under MAC with propofol; patient breathing spontaneously on nasal cannula.
MAC names the type of service, not a specific depth of sedation, which can range from light to deep. Because patients breathe on their own with an unprotected airway, obstruction and oversedation are the main risks. In anesthesia pharmacology MAC also stands for minimum alveolar concentration, and in infectious disease for Mycobacterium avium complex.
3. Media access control (address) (MAC)
Technology & Computing · Networking Abbreviations
A MAC address is the 48-bit hardware identifier assigned to every network interface, written as six pairs of hexadecimal digits such as 3C:22:FB:9A:10:4E. Switches use MAC addresses to deliver Ethernet and Wi-Fi frames within a local network; they are not routed across the internet.
Example: Add the TV's MAC to the router's allow list so it can join the network.
The first three bytes form the OUI, which the IEEE assigns to each manufacturer. Modern phones and laptops randomize their Wi-Fi MAC per network for privacy, which can break MAC filtering on routers. In security writing MAC can instead mean mandatory access control or message authentication code; a string of hex pairs or a mention of a network card points to the address. Unrelated to Apple's Mac computers.
4. Medicare Administrative Contractor (MAC)
Medical · Health Insurance Abbreviations
Private health insurer contracted by CMS to process Medicare Part A and Part B claims, or durable medical equipment claims, for a geographic jurisdiction. MACs pay providers, handle provider enrollment and first-level appeals and issue local coverage determinations.
Example: Claim denied by the MAC; filing a redetermination within 120 days.
MACs replaced the older fiscal intermediaries and carriers under the Medicare Modernization Act of 2003. A/B MACs and the four DME MACs cover separate jurisdictions. In anesthesia MAC means monitored anesthesia care, and in pharmacy contracts maximum allowable cost.
5. Minimum alveolar concentration (MAC)
Medical · Anesthesia Abbreviations
Concentration of an inhaled anesthetic in the lung alveoli, at one atmosphere, that prevents movement in response to surgical incision in 50 percent of patients. It is the standard measure of inhaled anesthetic potency: roughly 2 percent for sevoflurane, 6 percent for desflurane and 1.2 percent for isoflurane in adults.
Example: Sevoflurane at 0.8 MAC with a remifentanil infusion; BIS 45.
A lower MAC means a more potent agent. MAC falls by roughly 6 percent per decade of age and is reduced by opioids, pregnancy and hypothermia. Nitrous oxide has a MAC above 100 percent, so it cannot produce surgical anesthesia alone at normal pressure. Anesthesia workstations display age-adjusted MAC in real time.
6. Mycobacterium avium complex (MAC)
Medical · Infectious Disease Abbreviations
Group of environmental nontuberculous mycobacteria that cause disseminated infection in advanced HIV (CD4 below 50) and chronic lung disease in people with bronchiectasis or COPD. Treatment requires months of combination antibiotics, typically a macrolide, ethambutol and a rifamycin.
Example: Sputum cultures grew MAC three times with nodular bronchiectasis; start three-times-weekly therapy.
Lung disease in older, thin women without smoking history has been nicknamed "Lady Windermere syndrome". Organisms live in soil, water and showerheads and are not spread between people. In anesthesia MAC means monitored anesthesia care, and in women's health MAC can mean other things, so context is essential.
7. Material adverse change (MAC)
Law & Legal · Contract Abbreviations · also used in business
Contract clause, common in merger and loan agreements, that lets a party refuse to close or declare a default if the other party suffers a significant negative change in its business, financial condition or prospects. Lenders often make the absence of a MAC a condition to funding.
Example: The lender refused to fund the final tranche, claiming a MAC in the borrower's business.
MAC and MAE (material adverse effect) are often used interchangeably. Courts set a high bar: in IBP v. Tyson Foods (Del. Ch. 2001), the change had to be durationally significant, measured in years rather than months. Parties negotiate long lists of carve-outs, such as general economic conditions or pandemics, that cannot trigger the clause.
8. Maximum allowable cost (MAC)
Medical · Pharmacy Abbreviations
Upper limit a PBM or payer will reimburse a pharmacy for a generic drug, regardless of what the pharmacy paid. MAC lists are set privately by each PBM and updated frequently.
Example: Our MAC appeal on generic albuterol was denied, so we lose $12 per inhaler.
Many states now require PBMs to update MAC lists regularly and allow pharmacies to appeal when reimbursement is below acquisition cost. The federal Medicaid equivalent is the federal upper limit (FUL). MAC also means monitored anesthesia care and Mycobacterium avium complex.
9. Mandatory access control (MAC)
Technology & Computing · Cybersecurity Abbreviations
An access model in which a central policy, not the owner of a resource, decides who can access it, typically by comparing security labels such as Secret or Top Secret on users and data. Users cannot override or share access on their own.
Example: SELinux enforces MAC, so even root can't read files outside the policy's allowed labels.
Rooted in US military security models such as Bell-LaPadula (1973). SELinux, AppArmor and Windows integrity levels implement forms of it. It contrasts with discretionary access control, where owners grant permissions. MAC also names a network hardware address and a message authentication code; mentions of labels and policies point to this meaning.
10. Message authentication code (MAC)
Technology & Computing · Cybersecurity Abbreviations
A short tag computed from a message and a secret key that lets the recipient verify the message came from someone holding the key and was not altered. Secure network protocols attach one to every packet.
Example: The API rejects the webhook because the MAC in the signature header doesn't match.
Unlike a digital signature, a MAC uses a shared secret, so it proves integrity but not which of the key holders created it. HMAC, CMAC and Poly1305 are common constructions. In networking MAC refers to hardware addresses, and in access control to mandatory access control; keys and tags indicate the cryptographic meaning.
Related abbreviations
More computer abbreviations
- IT – Information technology
- ITIL – Information Technology Infrastructure Library
- ITSM – IT service management
- KB – Knowledge Base
- MBR – Master Boot Record
- MDM – Mobile device management
- MS-DOS – Microsoft Disk Operating System
- MSP – Managed service provider
See all 92 computer abbreviations →
More anesthesia abbreviations
- ISB – Interscalene brachial plexus block
- LA – Local anesthesia (local anesthetic)
- LAST – Local anesthetic systemic toxicity
- LMA – Laryngeal mask airway
- MH – Malignant hyperthermia
- NMB – Neuromuscular blockade (blocker)
- NORA – Non-operating room anesthesia
- PDPH – Post-dural puncture headache
See all 34 anesthesia abbreviations →
This entry is for general education and is not medical or legal advice. Abbreviation use varies between institutions; always confirm in context.