killerPronunciation: /ˈkɪlə/Translate killer | into French | into German | into Italian | into Spanish Definition of killer noun 1a person, animal, or thing that kills: [as modifier]:a killer virus 2 informal a formidable, impressive or difficult thing:his new novel is a killer a hilarious joke. 3Australian/NZ informal an animal that has been selected for slaughter. killer in other Oxford dictionaries Definition of killer in the US English dictionary