wedgie
The action of "wedging" (i. e. pulling) a garment or a piece of underwear so that a portion of its fabric is caught between the buttocks. This is typically considered an act of humiliation when done on others, but considered a sexually provocative act when it's performed by oneself.
Note that garments that naturally lie between the buttocks—such as thongs, fundoshi, and one-piece thongs—should not usually have this tag since the wedging is implied.
For garmets wedged between the labia, see frontal wedgie.
See also
The following tags implicate this tag: self_wedgie (learn more).