Entry 2 senses · 2 variants Webster, 1913 behaviorist · IPA /bɪhˈeɪvjərɪst/ n. adj. 01 n. a psychologist who subscribes to behaviorism. 1. a psychologist who subscribes to behaviorism. Syn. behaviourist. 02 adj. of, pertaining to, or characteristic of behaviorists or behaviorism. 1. of, pertaining to, or characteristic of behaviorists or behaviorism.