The definition of deathly is something that is related to or likely to cause death.
(adjective)A person who is extremely ill and likely to die is an example of someone who would be described as deathly ill.
See deathly in Webster's New World College Dictionary
adjective
Origin: ME dethlich < OE dēathlic: see death
adverb
See deathly in American Heritage Dictionary 4
adjective
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