deadly

Something that's deadly can kill you. Because a gun can end someone's life, it's a deadly weapon.

If someone's diagnosed with a deadly disease, it's lethal — it's capable of ending the person's life. When you hear someone talk about police officers using "deadly force," they mean actions that intended to cause death, or understood to be capable of killing someone. You can also use the word to mean "extremely" or "very," as when you describe your math class as deadly boring.

PRIMARY MEANINGS OF: deadly

1
adjadv
causing or capable of causing death
as if dead
2
adv
(used as intensives) extremely
FULL DEFINITIONS OF: deadly
1

adj causing or capable of causing death

“a deadly enemy”
Synonyms:
deathly, mortal
fatal
bringing death

adj of an instrument of certain death

deadly poisons”
Synonyms:
lethal
fatal
bringing death

adj exceedingly harmful

Synonyms:
baneful, pernicious, pestilent
noxious
injurious to physical or mental health

adj (of a disease) having a rapid course and violent effect

Synonyms
virulent
infectious; having the ability to cause disease

adj extremely poisonous or injurious; producing venom

Synonyms:
venomous, virulent
toxic
of or relating to or caused by a toxin or poison

adj involving loss of divine grace or spiritual death

“the seven deadly sins”
Synonyms:
mortal
unpardonable
not admitting of pardon

adv as if dead

Synonyms:
lifelessly
2

adv (used as intensives) extremely

deadly dull”
deadly earnest”
Synonyms:
deucedly, devilishly, insanely, madly
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