The Collaborative International Dictionary of English v.0.48:

Destroyer \De*stroy"er\, n. [Cf. OF. destruior.]
   1. One who destroys, ruins, kills, or desolates.
      [1913 Webster]

   2. (Nav.) a small fast warship used primarily as an escort to
      larger vessels and typically armed with a combination of
      5-inch guns, torpedos, depth charges, and missiles;
      formerly identical to the Torpedo-boat destroyer.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

destroyer
    n 1: a small fast lightly armored but heavily armed warship
         [syn: destroyer, guided missile destroyer]
    2: a person who destroys or ruins or lays waste to; "a destroyer
       of the environment"; "jealousy was his undoer"; "uprooters of
       gravestones" [syn: destroyer, ruiner, undoer, waster,
       uprooter]

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "destroyer":
   animal, annihilator, anthropophagite, arsonist, bane, barbarian,
   battleship, battlewagon, beast, biblioclast, bomber, brute, burner,
   can, cannibal, capital ship, demolisher, despoiler, destruction,
   dynamitard, dynamiter, exterminator, hun, hyena, iconoclast,
   idol breaker, idoloclast, man-eater, nihilist, ruin, ruination,
   ruiner, savage, shark, syndicalist, terrorist, tiger, undoing,
   vandal, wild man, wrecker



Easton's 1897 Bible Dictionary:

Destroyer
   (Ex. 12:23), the agent employed in the killing of the
   first-born; the destroying angel or messenger of God. (Comp. 2
   Kings 19:35; 2 Sam. 24:15, 16; Ps. 78:49; Acts 12:23.)