Pronunciation: (id"ē-u-sing'kru-sē, -sin'-),[key] —n., —pl.-sies. 1. a characteristic, habit, mannerism, or the like, that is peculiar to an individual.
2. the physical constitution peculiar to an individual.
3. a peculiarity of the physical or the mental constitution, esp. susceptibility toward drugs, food, etc. Cf. allergy (def. 1). Also,idiocrasy.