sloshing breasts
When a character's breasts make sloshing noises, as if there's liquid moving around within them - mostly used to imply a the breasts storing a large amount of breast milk (anatomically incorrect, but done with artistic licence), and/or to reinforce the large size of the character's breasts (sometimes for humorous effect), sloshing breasts most often occur when the character's breasts are moving. Often seen alongside lactation, breast expansion, and with characters who have huge or hyper breasts.
Do not tag if there are no written sound effects of the breasts sloshing - or if in an animation, no sound of the breasts sloshing. If there are only motion lines around the breasts, consider breast jiggle instead.