1. A groupie. Said of a woman who wantonly gives sexual favors for someone's attention. A "Kat Stacks" is usually scorned in the end and then becomes stalkerish.
2. A woman who desires something or someone to the point of absurdity, even when the desired object can't return the affection.
1. You went Kat Stacks on that chick man, you a herb!
2. Yo, she just Kat Stacked those shoes, she a herb!