deadlier; deadliest
1
: causing or able to cause death
deadly weapons
the world's most deadly snake
a more deadly form of the disease
They launched a deadly attack.
Officers are allowed to use deadly force if necessary.
2
: extremely accurate and effective
She shoots with deadly accuracy.
a basketball player with deadly aim
3
always used before a noun
: extreme or complete
A deadly silence followed his question.
The two gang leaders are deadly enemies.
He spoke with deadly seriousness.
4
informal
: very boring
The lecture was pretty deadly.
deadlier; deadliest
: extremely or completely
He's deadly [=dead] serious about finding another job.
a deadly boring/dull meeting
Cite this Entry
“Deadly.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/deadly. Accessed 15 Apr. 2026.
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