The (often provocative) arching of the lower region of the back, making the lumbar area "hollow" - thus 'hollaback'. This action thrusts both the buttocks and chest area out, and is a classic cockteaser pose.
Lookit that hollaback girl! Stickin' her ass an' tits out...I'm goin' to take her from behind, man! She WANTS it from behind, that hollaback girl!
by Asoz Asis July 30, 2005