Clothing that is unrealistically skin tight, especially between and beneath the breasts. Normal clothing does not hug the breasts on all sides. Impossible clothing hugs the body in ways that normal clothing could never do.
Although this is most commonly seen with breasts, it may also occur with other body parts (post #352925).
See tight clothes or skin tight for clothing that is very tight, but not unrealistically so.
The Japanese term is 乳袋 (chichi-bukuro, lit. "breasts sack").
