This statement is usually used as verbal sexual
harassment for the purpose of an attempt
at seduction. The statement implies lending the speaker the use of one's ass, presumably
for sex. In a sentence, this is most effective when shouting from a distance, such as from a moving car, or the second story
of a building.
Four men are riding in a car. One see an attractive female, but knows he cannot
her for reals, so he decides to shout out to window at her. His statement of choice is "Gurrrrl, let me get some booty
up off you!"
As the girl
turns, he receives some self-satisfaction.