attagirl(redirected from that a girl)
An expression of encouragement, support, or approval toward a girl, woman, or female animal, used as a standalone interjection before or after a sentence. Largely presumed to be a corruption of the expression "that's the girl"; it is also sometimes spelled "atta girl." Attagirl! I knew you would ace your exam.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.