The Collaborative International Dictionary of English v.0.48:

Hot-head \Hot"-head`\, n.
   A violent, passionate person; a hasty or impetuous person;
   as, the rant of a hot-head.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hothead
    n 1: a belligerent grouch [syn: fire-eater, hothead]
    2: a reckless impetuous irresponsible person [syn: daredevil,
       madcap, hothead, swashbuckler, lunatic, harum-
       scarum]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "hothead":
   Mafioso, Tartar, Young Turk, bear, beast, beldam, berserk,
   berserker, bomber, brute, crank, crosspatch, demon, devil, dragon,
   feist, fiend, fire-eater, firebrand, fury, goon, gorilla,
   grizzly bear, grouch, gunsel, hardnose, hell-raiser, hellcat,
   hellhound, hellion, holy terror, hood, hoodlum, hotspur,
   incendiary, killer, mad dog, madcap, monster, mugger, rapist,
   revolutionary, savage, she-wolf, sorehead, spitfire, termagant,
   terror, terrorist, tiger, tigress, tough, tough guy, ugly customer,
   violent, virago, vixen, wild beast, witch, wolf