A) A very vertical wave face where the crest or lip of the wave throws forward to create a tube or barrel. B) Also used to describe a swell which is approaching a forecast location at a very sharp angle compared to the direction the coastline faces. The incoming swell energy may be just on the edge of the swell window, which usually means only the very best exposed breaks to the incoming swell, will be able to pick it up. C) A term used by the National Data Buoy centre (NDBC) to describe the dominant sea state at a buoy. For a given wave height, steep waves represent a more serious threat to capsizing vessels or damaging marine structures than broad swell.