BOYISH
boyish, boylike, schoolboyish
(adjective) befitting or characteristic of a young boy; “a boyish grin”; “schoolboyish pranks”
Source: WordNet® 3.1
Etymology
Adjective
boyish (comparative more boyish, superlative most boyish)
Like a stereotypical boy in appearance or demeanor.
Source: Wiktionary
Boy"ish, a.
Definition: Resembling a boy in a manners or opinions; belonging to a boy;
childish; trifling; puerile.
A boyish, odd conceit. Baillie.
Source: Webster’s Unabridged Dictionary 1913 Edition