Bad Temper is a mental, mundane disadvantage, described in Basic Set, p. 124, and referenced in GURPS Dungeon Fantasy 10: Taverns™, p. 11, on its role in starting bar fights.
Sean Punch has commented on Bad Temper in the following post to the SJG GURPS Forums:
Ad blocker interference detected!
Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers
Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.