A device that may assume either one of two reversible, stable states. Note 1: The flip-flop is used as a basic control element in computer and communications systems. Note 2: In a flip-flop, the transition from one stable state to the other is unstable, i.e., for the very short period during which the transition takes place, both outputs may assume the same state, which state may be unpredictable. Synonyms bistable circuit, bistable multivibrator, bistable trigger circuit.