Stupor is a state of altered consciousness characterized by deep sleep or unresponsiveness, susceptible to arousal only by vigorous and/or repeated stimuli, with lapse back into unresponsiveness when the stimulus stops. Stupor is a less severe impairment of conscious level than coma, but worse than obtundation (torpor). It is suggestive of diffuse cerebral dysfunction, e.g., drug-induced.
Plum F, Posner JB. The diagnosis of stupor and coma (3rd edition). Philadelphia: FA Davis, 1980