Definition of "killer" in English

noun

1. One who or that which kills.

   • There’s a killer on the loose.
   • My cat is a habitual bird killer.
   • Carbon monoxide is a silent killer.

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

   • That test was a killer.
   • The final hill in the race course was a killer.

3. (figuratively) Something that is so far ahead of its competition that it effectively kills off that competition.

   • Digital streaming platforms are CD killers.

4. (figuratively) A remarkably impressive person or thing.

5. (sports, uncountable) A knockout form of darts or pool involving several players.

6. Ellipsis of killer whale.

7. A club used for killing fish.

8. (philately) A particularly heavy type of handstamp, or portion of one, often obscuring a large part of the postage stamp.

9. Synonym of virama (“kind of diacritical mark”).

adjective

1. (slang) Excellent, very good, cool.

   • killer feature
   • killer view

2. Causing death, destruction, or obliteration.

   • killer bee
   • killer robot

3. Distressing, uncomfortable.

   • I had a killer headache this morning.