interj.
Informal. Used to show encouragement or approval to a boy or man: Attaboy! That's the way to hit a home run!
[Alteration of That's the boy!.]
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
