Skeg meaning : A fin-like structure to the rear of the keel of a vessel that supports the rudder and protects a propeller. A similar construction on a boat that acts as a keel. A fin that serves to stabilize a surfboard. A surfer; a person who leads a surfing lifestyle. A sort of wild plum (Prunus spinosa or Prunus domestica subsp. insititia (syn. Prunus institia)). A kind of oat.