Dictionary

One who or that which kills.

Example: Carbon monoxide is a silent killer.

That which causes stress or is extremely difficult, especially that which may cause failure at a task.

Example: That test was a killer.

Something that is so far ahead of its competition that it effectively kills off that competition.

Example: Digital streaming platforms are CD killers.

A knockout form of darts or pool involving several players.

Excellent, very good, cool.

Example: killer feature

Causing death, destruction, or obliteration.

Example: killer bee

Distressing, uncomfortable.

Example: I had a killer headache this morning.

A sea mammal related to dolphins and porpoises (Orcinus orca).