noun
1. predatory black-and-white toothed whale with large dorsal fincommon in cold seas
Synonym: killer whaleorcagrampussea wolfOrcinus orca
2. a difficulty that is hard to deal with
e.g. that exam was a real killer
3. someone who causes the death of a person or animal
Synonym: slayer
4. the causal agent resulting in death
e.g. heart disease is the biggest killer in the United States
Synonym: cause of death