A 'wedgie' is the simple, yet painful manoeuvre of pulling another's underwear up at the back so that the bottom part gets wedged firmly and painfully up the victim's anus. Traditionally, the wedgie is accompanied by a loud shout of 'Wedgie-eeeeeeeeee!', just in case the victim failed to notice that they were being wedgied. There are varying versions of the wedgie. These are:
The Regular Wedgie: This one is usually applied when the purpose is embarrassment, or during a friendly fight. The wedgier simply moves behind, grabs the underwear and yanks it up, usually until the victim has begged for mercy long enough.
The Vicious Wedgie: This is not done in the best of spirits. As before, the wedgier grabs the underwear, but will continue to apply the wedgie until the underwear rips. The attacker may also lift the victim up in the air by the underwear band to inflict extra pain. A terrible business.
The Cheap Shot Wedgie: As its name suggests, the attacker sneaks up, administers a quick, yet firm wedgie and then legs it.
The Cloakroom Wedgie: Used as a bullying tactic not so long ago in English primary schools, the attacker wedgies the victim, then hangs the band of the underwear on a useful implement nearby and leaves them there, hanging by their underwear until:
Someone comes and rescues them.
They somehow unhook themselves.
Their underwear splits and they fall to the floor.
The Cheese Wedgie: Used only in cartoons, the wedgier comes in from behind and hooks the underwear over the victim's head. The character 'The Mask' uses the Cheese Wedgie regularly.
In organised bullying, the wedgie is sometimes used along with other techniques - for example, someone being very large running into the little kids toilets, Cloakroom Wedgying them onto the coat-hanger (yes, some toilets have coat-hangers), then performing the time-honoured act of shoving their face down the toilet bowl and flushing.
So all in all, a wedgie is definitely something to be avoided at all costs.