Breast that initiate or increase one's desire to touch, grasp and have one's way with, when seen bouncing as a result of jumping or jumping-like movements.
Jack: I never noticed Jenny had such large and shapely breasts until I saw her jumping on that trampoline.
Brad: Yeah, me too! She has mad jump jugs.
"I'd always liked Jessica's breasts but when I saw her jump jugs in that aerobics class my desire to have my way with them increased exponentially."