Succinctly, breasts in a tight sweater.
Also, sweater muffins, sweater meat, sweater puppies, etc.
One of the many names internet people call breasts; you are unlikely to encounter this term outside the internet and if you use it outside the internet you are less likely to be understood.
A lame neologism. There are better words for breasts.
Bombshells, Gazingas, Milk Fountains, Milk Shakes, Molehills, Spheres of Venus, Knockers, Mommas, Globes, Mondos,the Twins, Boobies, Montezumas, Gongas, the girls, Moo Moos, and Sweater Stuffers.