A peculiarity of physical or mental constitution or temperament; a characteristic belonging to, and distinguishing, an individual; characteristic susceptibility; idiocrasy; eccentricity.
"An Eccentricity of Character or Behavior." From the Greek "idiosynkrasia" of the same meaning. The Greek word developed from "idios" = "private or personal" and "synkrasis," which translates roughly to "admixture" from "syn" = "together" and "krasis" = "mixture." See also "idiotsyncrasy."
a behavioral attribute that is distinctive and peculiar to an individual