† idioˈsyncrasisObs.rare. [a. Gr. ἰδιοσύγκρᾱσις.] = next. 1654Whitlock ZootomiaPref. a iij, Out of an Idiosyncrasis (or particular Temper) of my Fancy.1797Monthly Mag. III. 348 Lest the acrid humour..should be mistaken for the effect produced by an idiosyncrasis of the vessels.