incapable

Etymology

Borrowed from Middle French incapable, in- + capable.

adj

1. Not capable (of doing something); unable.
   A pint glass is incapable of holding more than a pint of liquid.
   I consider him incapable of dishonesty.
   The British people seem incapable of avoiding the habit of leaving litter wherever they go, and the railways certainly seem to receive their fair share of it, in carriages and on stations. 1962 October, Brian Haresnape, “Focus on B.R. passenger stations”, in Modern Railways, page 254
2. Not in a state to receive; not receptive; not susceptible; not able to admit.
   incapable of pain, or pleasure; incapable of stain or injury

noun

1. (dated) One who is morally or mentally weak or inefficient; an imbecile; a simpleton.