Source : Webster's Revised Unabridged Dictionary (1913)

Mental \Men"tal\, a. [L. mentum the chin.] (Anat.)
   Of or pertaining to the chin; genian; as, the mental nerve;
   the mental region.

Mental \Men"tal\, n. (Zo["o]l.)
   A plate or scale covering the mentum or chin of a fish or
   reptile.

Mental \Men"tal\, a. [F., fr. L. mentalis, fr. mens, mentis, the
   mind; akin to E. mind. See {Mind}.]
   Of or pertaining to the mind; intellectual; as, mental
   faculties; mental operations, conditions, or exercise.

         What a mental power This eye shoots forth! --Shak.

   {Mental alienation}, insanity.

   {Mental arithmetic}, the art or practice of solving
      arithmetical problems by mental processes, unassisted by
      written figures.

Source : WordNet®

mental
     adj 1: involving the mind or an intellectual process; "mental
            images of happy times"; "mental calculations"; "in a
            terrible mental state"; "mental suffering"; "free from
            mental defects" [ant: {physical}]
     2: of or relating to the mind; "mental powers"; "mental
        development"; "mental hygiene"
     3: of or relating to the chin- or lip-like structure in insects
        and certain mollusks
     4: of or relating to the chin or median part of the lower jaw
        [syn: {genial}]
     5: affected by a disorder of the mind; "a mental patient";
        "mental illness"