burn·out / ˈbərnˌout/ • n. 1. the reduction of a fuel or substance to nothing through use or combustion.2. physical or mental collapse caused by overwork or stress: high levels of professionalism that may result in burnout. ∎ inf. a dropout or drug abuser, esp. a teenage one.3. failure of an electrical device or component through overheating: an antistall mechanism prevents motor burnout.