Source : Webster's Revised Unabridged Dictionary (1913)

Childish \Child"ish\, a.
   1. Of, pertaining to, befitting, or resembling, a child.
      ``Childish innocence.'' --Macaulay.

   2. Puerile; trifling; weak.

            Methinks that simplicity in her countenance is
            rather childish than innocent.        --Addison.

   Note: Childish, as applied to persons who are grown up, is in
         a disparaging sense; as, a childish temper.

Source : WordNet®

childish
     adj : indicating a lack of maturity; "childish tantrums";
           "infantile behavior" [syn: {infantile}]