floor dusters 

Elongated, saggy breasts most often found on older women.

Man, look at Linda's floor dusters swinging away while she walks.

floor dusters by TFT152 June 30, 2011

floordusters 

Breasts that are so large that they'll end up saggin below the knees - dusting the floor.

Yeah, Amber's got huge knockers, but when she turns 40, and has had a few kids I'll bet they'll be floordusters.

floordusters by Leif June 10, 2006