adj
deadly
DEHD-lee
adj
1
Capable of causing death.
"The snake's venom is deadly if left untreated."
"A deadly combination of speed and ice caused the crash."
2
Extremely accurate or effective.
"His serve was deadly all through the tournament."
adv
1
Extremely; used to intensify an adjective.
"The meeting was deadly boring."
How to Use Deadly
Learner’s notesIn plain EnglishAble to kill, or (informally) extremely something — usually extremely boring or extremely skilled.
Common pairings
deadly weapon
deadly virus
deadly accurate
deadly serious
Word Forms
deadlier comparative, more deadly comparative, more deadly comparative, deadliest superlative, most deadly superlative, most deadly superlative
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The snake's venom is _____ if left untreated.
Etymology
From Old English deadlic, built from dead plus -lic (the ancestor of -ly), literally "death-like".