In surfing, the lip is the breaking part of a wave that pitches or throws forward into a barrel.
As a wave steepens, its upper edge begins to curl over. Surfers call this moving edge the lip. When the lip throws over the hollow space beneath it, the result is commonly called a barrel, tube, or green room. Riding inside that space is one of surfing’s most celebrated maneuvers.
The lip is different from the shoulder, which is the unbroken or less steep part of the wave extending away from the breaking section. The peak is generally the highest or first breaking part of a wave, while the channel is a deeper area often used for paddling back out.
Surfing commentary often describes a surfer hitting, ducking under, or getting clipped by the lip. The exact shape and force of the lip depend on swell direction, tide, wind, and the sea floor.