noun thi·o·nyl \ˈthīənəl, -ˌnil\

Definition of thionyl



  1. :  the bivalent radical or cation >SO of sulfurous acid :  sulfinyl —used especially in names of inorganic compounds

Love words? You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Join MWU now and get access to America’s largest dictionary, with:

  • 300,000 words that aren't in our free dictionary
  • Expanded definitions, etymologies, and usage notes
  • Advanced search features
  • Ad free!

Origin and Etymology of thionyl

International Scientific Vocabulary 1thion- + -yl; originally formed in German

Seen and Heard

What made you want to look up thionyl? Please tell us where you read or heard it (including the quote, if possible).


to cast off or become cast off

Get Word of the Day daily email!