Definition: (Noun) When the crest (or lip) of a breaking wave curls over and around a surfer, the resulting situation creates an open area within the wave through which the rider can navigate. This is the epitome, pinnicle, and all-time golden moment in surfing. This, my friends, is a tube.
Also Known As: barrel, shack, green room, deep throat (I think I just made this one up)
Examples:The waves were so hollow yesterday that I got a 6 second tube.