Compressed aerated water that blasts out horizontally from the mouth of a hollow wave. As the ceiling and walls of the wave's tubing interior collapse, a bellows effect is created and for two or three seconds a mixture of air and water are funneled out of the tube opening. If a surf break has spitting waves with good form, it's a tuberiding day. Pipeline and Teahupoo, two of the world's best-known tuberiding breaks, both spit regularly and prodigiously.
The amount of spit isn't so much a function of the span and breadth of the tube, but the wave's thickness and power. A thin, circular tube may produce a gentle puff of spit, while a broad-based, solid-lipped tube can belch spit with enough force to temporarily blind the surfer inside, sting his back and neck, and even lift him off the surface of the wave.
A wave can spit more than once, and a long, hollow point wave—like Kirra or Skeleton Bay—might spit three or four times from start to finish. The phrase "spitting peak" is used to describe a symmetrical wave that tubes and spits in both directions.