When someone, i.e. a man, has a big beard very similar to the pitcher Brian Wilson and he uses his man beard on a girls clitoris in a vigorous up and down or side to side motion for an extended period of time till she gets off. That said girl has now become "Brian Wilson-ed".

A pubic hair piece. A toupee for the pubic area/genitals. In the 1700’s when mercury was used to treat sexually transmitted diseases (Gonorrhea or Syphilis) one of the side effects was the loss of pubic hair. To disguise this condition, that was not cured by mercury, a Merkin was employed.

The action at which someone screws you over on purpose out of pure jealousy and anger