(a.) Phrase, to be employed by either men or women, used to compliment a woman's impressive breasts and their power over others.
(b.) Phrase employed by the owner of said impressive breasts, as a way of increasing her status or just plain bragging.
Person 1: Daaamn, check out Kirsten's tits!
Person 2: Srsly, respect the rack on that one
Woman with small tits: Aww man, I'm only an A cup.
Woman with big tits: *chuckles* Respect the rack, hun.