idiosyncrasynoun · Level 3 SAT1A mental quality or habit peculiar to an individualHis most endearing idiosyncrasy was his habit of humming folk songs whenever he was working through a difficult problem.ModuleLevel 3RegisteracademicCollectionCollection 042SAT Complete planAlso in Collection 042incoherence, preference, periphrasis, mutableness, threnody, gentile, apologue, habituation and 1 more