a combining form meaning “tumor,” “mass,” used in the formation of compound words: oncogenic.

Nearby words

  1. once-over-lightly,
  2. oncer,
  3. onchocerca,
  4. onchocerciasis,
  5. oncidium,
  6. oncocyte,
  7. oncocytic hepatocellular tumor,
  8. oncocytoma,
  9. oncofetal,
  10. oncofetal antigen

Origin of onco-

combining form of Greek ónkos mass, bulk

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for onco-


combining form

denoting a tumouroncology

Word Origin for onco-

from Greek onkos

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for onco-


word-forming element meaning "bulk, mass," especially in medical use, "tumor," from Latinized form of Greek onko-, comb. form of onkos "bulk, size, mass, body."

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for onco-



Mass; swelling:oncolysis.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.