An acronym for Tight Little Boys Ass. Although it sounds weird and perverted, it's actually used to describe a woman's ass. These women (aka Nicky G Style girls) are typically smaller in proportion to the average female, and therefore have smaller asses. Therefore, the term TLBA is used to describe just how small and tight their asses are.
Maggie: Describe your perfect woman.
Davey: 5'4", brown hair, blue eyes, nice breasts...you know...not too big and not too small, and just like a tight little boys ass (TLBA).
(silence overcomes the room...)