A person or thing that causes death or destruction; one who kills or is responsible for killing someone or something. noun
The murderer was identified as a notorious killer.
The killer whale is also known as an orca.
Something that is extremely effective or impressive, often in a way that is overwhelming or unbeatable. adjective
That new smartphone is a killer device with incredible features.
Her performance in the game was a killer, securing her victory.
A person or thing that defeats or outperforms others decisively. noun
The team was a killer on the field, winning every match.
This new software is a killer app that revolutionizes the industry.