noun (n)

• device that heats water or supplies warmth to a room(noun.artifact)

  Synonym:
  warmer
  

  source: wordnet30
• (baseball) a pitch thrown with maximum velocity(noun.act)

  Synonym:
  bullet, fastball, hummer, smoke
  

  source: wordnet30
• One who, or that which, heats.(noun)

  source: webster1913