Noun

• S: (n) killer, slayer (someone who causes the death of a person or animal)
• S: (n) cause of death, killer (the causal agent resulting in death) "heart disease is the biggest killer in the United States"
• S: (n) killer (a difficulty that is hard to deal with) "that exam was a real killer"
• S: (n) killer whale, killer, orca, grampus, sea wolf, Orcinus orca (predatory black-and-white toothed whale with large dorsal fin; common in cold seas)