n. (pl. -ies) 1 a mental constitution, view or feeling, or mode of behaviour, peculiar to a person. 2 anything highly individualized or eccentric. 3 a mode of expression peculiar to an author. 4 Med. a physical constitution peculiar to a person. idiosyncratic adj. idiosyncratically adv.
[ Gk idiosugkrasia f. idios own + sun together + krasis mixture ]