a hairstyle in which the sides and back are shaved and long hair is grown at the top of the head

to weaken, damage, or cause the failure of something; undermine:

A strategic move in racing to get past the car in front without actually overtaking it on track. The car behind will pit earlier, do a quick lap on fresh tyres and come out in front once the other car has pitted.

A hairstyle that has been in existance for quite awhile. now branded popular by the dubstep artist Skrillex. Many guys and girls have been randomly on whim deciding to shave one side of their head, do to its growing popularity in the dubstep crowd.

Sadly, only a handful of individuals can actually pull this hair-do off. Leaving a majority of the hip-crowd who think it looks cool thanks to the fame of a certain Sonny Moore, look fairly odd, or unattractive(including Skrillex himself).

A very common sort of haircut worn by people with opinions. Often associated with bands like 36 Crazyfists, Avenged Sevenfold, and Dredg. Excessive use of undercuts in association with strumming of chords can cause sudden precipitation, even inside. See also dyess

A sexual innuendo

/ˌəndərˈkət ˈsinˌdrōm/

noun
When a female with short hair, or an undercut, has obsessively loved a person who does not love them back.