What is a skag?

Answer 1

A scag is someone who is skankified angry aggressive person, someone who is pissed off easy . gets angry a lot and or easily, is frustrated a lot , whines, is moody.

Also a scag is someone who is scum or nasty.

Answer 2

A skeg (or skag) is a sternward extension of the keel of boats and ships which have a rudder mounted on the centre line. The term also applies to the lowest point on an outboard motor or the outdrive of an inboard/outboard. In more recent years, the name has been used for a fin on a surfboard which improves directional stability and to a moveable fin on a kayak which adjusts the boat's centre of lateral resistance.

From: http://en.wikipedia.org/wiki/Skeg