Entry 2 senses · 2 variants Webster, 1913 auto /ôt'-ō/ · au·to · IPA /ˈɔtoʊ/ n. a. 01 n. An abbreviation of automobile. 1. An abbreviation of automobile. Also: automobile Syn. car, automobile, machine, motorcar 02 a. of or pertaining to an automobile; as, an auto mechanic. 1. of or pertaining to an automobile; as, an auto mechanic.