What is the meaning of Killer?

One who or that which kills.

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

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

A remarkably impressive person or thing.

A knockout form of darts or pool involving several players.

Ellipsis of killer whale.

A club used for killing fish.

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

Synonym of virama (kind of diacritical mark)

Excellent, very good, cool.

Causing death, destruction, or obliteration.

Distressing, uncomfortable.

professor who is known for often giving students failing grades

Mafia (party game)

comparative degree of kil

hitman (hired assassin)

murderer, assassin

Clipping of serial killer (serial killer).

feminine dative of kill

Source: wiktionary.org