From 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.]