A "wedgie" is a playful term used to describe a prank where someone's underwear is pulled up from behind, usually causing discomfort and embarrassment. The action typically involves yanking the underwear upwards so it rides up against the person's body. While often carried out among friends or peers in a lighthearted manner, it can sometimes be unwelcome and considered bullying if done without consent.
The term "wedgie" is believed to have originated in the United States in the mid-1980s and is a colloquial diminutive of "wedge," referring to how the underwear is wedged between the person's body and their clothing during the act. The playful nature of the word likely contributed to its popularity.