Outside legal spheres, the word "traitor" may also be used to describe a person who betrays (or is accused of betraying) their own political party, nation, family, friends, ethnic group, team, religion, social class, or other group to which they may belong. Often, such accusations are controversial and disputed, as the person may not identify with the group of which they are a member, or may otherwise disagree with the group members making the charge.
http://en.wikipedia.org/wiki/Treason