Booters is a combination of two words, booty and hooters. It can have two connotations, positive or negative. It can refer to the positive, which is an ass so perky and tight that it resembles a pair of breasts or the negative, which is a pair of breasts so saggy and nasty that they resemble an ass.
Positive: "Damn...Michelle has some nice booters."
Negative: "Holy shit...that chick had some ugly ass booters."