Source : Webster's Revised Unabridged Dictionary (1913)

Boyish \Boy"ish\, a.
   Resembling a boy in a manners or opinions; belonging to a
   boy; childish; trifling; puerile.

         A boyish, odd conceit.                   --Baillie.

Source : WordNet®

boyish
     adj : befitting or characteristic of a young boy; "a boyish grin";
           "schoolboyish pranks" [syn: {boylike}, {schoolboyish}]