Defined by the actions of former American Idol contestant Adam Lambert onstage, in which he grasped a dancer by the back of the head. He then proceeded to shove the dancer's face into his groin, and thrust his hips vigorously.
The action of thrusting one's hips into someone's face is now known as a "Lambert".
Man, that girl's a butterface! It's a good thing I don't have to look at it when I lambert her.