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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."
by O.A.O. December 12, 2009