Entry 1 sense Webster, 1913 Idiosyncratic /ĭdˌ-ē-ōs-ĭnˌ-krăt'-ĭk/ · Id·i·o·syn·crat·ic · IPA /ˌɪd.i.oʊ.sɪŋˈkɹæt.ɪk/ 01 a. Of peculiar temper or disposition; belonging to one's peculiar and individual character. 1. Of peculiar temper or disposition; belonging to one's peculiar and individual character.