skeg

Short definition from Wiktionary

Noun

1. 1
   A fin-like structure to the rear of the keel of a vessel that supports the rudder and protects a propeller.
2. 2
   A similar construction on a boat that acts as a keel.
3. 3
   A fin that serves to stabilize a surfboard.
4. 4
   A surfer; a person who leads a surfing lifestyle.
5. 5
   A sort of wild plum (Prunus spinosa or Prunus domestica subsp. insititia (syn. Prunus institia)).
6. 6
   A kind of oat.
7. 7
   A look or glance.