idiocy Meaning, Definition & Usage

  1. noun extreme mental retardation
    amentia.

WordNet

Id"i*o*cy noun
Etymology
From idiot; cf. Gr. uncouthness, want of education, fr. . See Idiot, and cf. Idiotcy.
Definitions
  1. The condition or quality of being an idiot; absence, or marked deficiency, of sense and intelligence.
    I will undertake to convict a man of idiocy, if he can not see the proof that three angles of a triangle are equal to two right angles. F. W. Robertson.

Webster 1913