Noun
A sort of wild plum.
A kind of oats.
The after part of the keel of a vessel, to which the rudder is attached.
Source: Webster's dictionaryBoth forms of sailing may employ the airfoil in a manner that provides an upward force, as well as a propulsive one, when the sailor controls the airfoil atop a planing board with a skeg. Source: Internet
Since the skeg sticks out below the hull of the boat it is the most vulnerable to damage, however it is relatively easy to replace skegs by gluing a new one on. Source: Internet