What is Tits-a-floppin?
1.
(phrase): a term for female (or some male) mammary glands, often referred to as breasts, that are sagging to the floor due to the force of gravity and bounces in a flopping manner every time the owner of said glands are moving.
(n.): a nickname for someone whose tits are flopping
(phr): your grandma's tits-a-floppin and hit me in the face