A follower of the theories or methods of B. F. Skinner WordNet 3.0 & Open English WordNet

A person who endorses the behavioristic tradition of B. F. Skinner, that is, psychology should study the conditions under which behavior occurs, and that behavior is observable and measurable, as are the environmental conditions that control it. Wiktionary

Endorser of B. F. Skinner’s behaviorist psychology. Wiktionary (translation)