Definition of "deathly"

deathly

/ˈdɛθli/

adjective
comparative deathlier or more deathly, superlative deathliest or most deathly
1. Appearing as though dead, or on the verge of death.
  Quotations
  I rushed towards her, and embraced her with ardour; but the deathly languor and coldness of the limbs told me, that what I now held in my arms had ceased to be the Elizabeth whom I had loved and cherished.
  1818, [Mary Shelley], chapter VI, in Frankenstein; or, The Modern Prometheus. […], volume III, London: […] [Macdonald and Son] for Lackington, Hughes, Harding, Mavor, & Jones, page 120
2. Deadly, fatal, causing death.
3. Extreme.
adverb
comparative more deathly, superlative most deathly
1. In a way that resembles death.
2. Extremely, dreadfully.