Killer \Kill"er\, n.

1. One who deprives of life; one who, or that which, kills. [1913 Webster]

2. (Zool.) A voracious, toothed whale of the genus Orca, of which several species are known; called also killer whale. [1913 Webster]

Note: The killers have a high dorsal fin, and powerful jaws armed with large, sharp teeth. They capture, and swallow entire, large numbers of seals, porpoises, and dolphins, and are celebrated for their savage, combined attacks upon the right whales, which they are said to mutilate and kill. The common Atlantic species (Orca gladiator), is found both on the European and the American coast. Two species (Orca ater and Orca rectipinna) occur on the Pacific coast. [1913 Webster]

Source: The Collaborative International Dictionary of English v.0.48
 

103 Moby Thesaurus words for "killer": Bluebeard, Cain, Mafioso, Young Turk, apache, assassin, assassinator, beast, beldam, berserk, berserker, bloodletter, bloodshedder, bomber, bravo, brute, bucko, bully, bullyboy, burker, butcher, button man, cannibal, cutthroat, daisy, demon, desperado, devil, dilly, dragon, eradicator, executioner, exterminator, fiend, fire-eater, firebrand, fury, garroter, goon, gorilla, gun, gunman, gunsel, hardnose, hatchet man, head-hunter, hell-raiser, hellcat, hellhound, hellion, hit man, holy terror, homicidal maniac, homicide, hood, hoodlum, hooligan, hothead, hotspur, humdinger, incendiary, lulu, mad dog, madcap, man-eater, man-killer, manslayer, massacrer, matador, monster, mugger, murderer, pesticide, poison, poisoner, rapist, revolutionary, rough, rowdy, ruffian, savage, she-wolf, slaughterer, slayer, spitfire, strangler, termagant, terror, terrorist, thug, tiger, tigress, torpedo, tough, tough guy, trigger man, ugly customer, violent, virago, vixen, wild beast, witch, wolf

Source: Moby Thesaurus II by Grady Ward, 1.0
 

killer

Source: WordNet (r) 2.0
 

Killer \Kill"er\, n.

1. One who deprives of life; one who, or that which, kills.

2. (Zo["o]l.) A voracious, toothed whale of the genus Orca, of which several species are known.

Note: The killers have a high dorsal fin, and powerful jaws armed with large, sharp teeth. They capture, and swallow entire, large numbers of seals, porpoises, and dolphins, and are celebrated for their savage, combined attacks upon the right whales, which they are said to mutilate and kill. The common Atlantic species (Orca gladiator), is found both on the European and the American coast. Two species (Orca ater and O. rectipinna) occur on the Pacific coast.

Source: Webster's Revised Unabridged Dictionary (1913)