Noun

1. One who is left-handed, especially in sports.
2. A left-handed pitcher.

   Since home plate is generally in the southwest corner to avoid glare in the batter's eyes, a southpaw's pitching hand is to the south.

3. A left-handed writer who, instead of mirroring right-handed writers, turn his or her hand upsidedown in order to put the writing implement in the same position as right-handed writers.