noun

a serious, unexpected, and often dangerous situation requiring immediate action.

personal alarms for use in an emergency

crisis,urgent situation,extremity,exigency,accident,disaster,catastrophe,calamity,difficulty,plight,predicament,tight spot,tight corner,mess,quandary,dilemma,unforeseen circumstances,dire/desperate straits,danger,scrape,jam,fix,pickle,spot,hole,hot water,crunch,panic stations