Clipping of mackintosh (“a raincoat”).

(Canada, US, slang) Clipping of macaroni.

(US, informal) Used to address a man whose name is unknown.

(Irish and Scottish patronymic surnames) son of.

A diminutive of the male given name Max. / (US, Canada) A diminutive for a person with a surname that starts with "Mac" or "Mc".

A Macintosh computer (made by Apple Inc.).

(informal) McMaster University

(US military) Acronym of Military Airlift Command, formerly, one of three former divisions of the US airforce, the others being SAC and TAC. / Acronym of Military Armament Corporation.

(chemistry) Initialism of maximum allowable concentration, the maximum concentration of a pollutant which is considered harmless to healthy adults during their working hours, assuming they breathe uncontaminated air at all other times.

Abbreviation of Macedonian. (South Slavic language)