From Middle English dethlich, from Old English dēaþlīċ, equivalent to death +‎ -ly.

• (UK) IPA^(key): /ˈdɛθli/

• Audio (Southern England):

  (file)

• Rhymes: -ɛθli

deathly (comparative deathlier or more deathly, superlative deathliest or most deathly)

1. Appearing as though dead, or on the verge of death.

   He has a deathly pallor.

   • 1816 June – 1817 April/May (date written), [Mary Shelley], chapter VI, in Frankenstein; or, The Modern Prometheus.[…], volume III, London: […] [Macdonald and Son] for Lackington, Hughes, Harding, Mavor, & Jones, published 1 January 1818, →OCLC, page 120:

     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.

2. Deadly, fatal, causing death.
3. Extreme.

   He has a deathly fear of crocodiles.

• deathly pale

deathly (comparative more deathly, superlative most deathly)

1. In a way that resembles death.

   He was deathly pale.

2. Extremely, dreadfully.

   The water was deathly cold.

   He was deathly afraid of crocodiles.

   • 2025 December 21, Esther Zuckerman, “Is Sydney Sweeney Today’s Most Perplexing Movie Star?”, in The New York Times‎^[1], New York, N.Y.: The New York Times Company, →ISSN, →OCLC:

     And indeed, [Sydney] Sweeney’s quotes are deathly dull. On changing her body for “Christy,” she said: “It’s so fun just not being yourself.”

     (Can we archive this URL?)