Attaboy

Alternative forms

 * atta boy

Etymology
Alteration of "that's a boy!" or "that's the boy!".

Interjection

 * 1)  Used to show encouragement or approval to a boy or man.
 * Attaboy! That's the way to hit a home run!

Noun

 * 1) A cry of "attaboy"; an accolade.