a combining form meaning “breast,” used in the formation of compound words: mastopathy.

Nearby words

  1. mastigophoran,
  2. mastigote,
  3. masting,
  4. mastitic,
  5. mastitis,
  6. masto-occipital,
  7. mastocarcinoma,
  8. mastocyte,
  9. mastocytoma,
  10. mastocytosis

Also especially before a vowel, mast-.

Origin of masto-

combining form representing Greek mastós breast Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for masto-


before a vowel mast-

combining form

indicating the breast, mammary glands, or something resembling a breast or nipplemastodon; mastoid

Word Origin for masto-

from Greek mastos breast

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 masto-


before vowels mast-, word-forming element meaning "breast," from comb. form of Greek mastos "woman's breast," from madan "to be wet, to flow," from PIE *mad- "wet, moist, dripping" (cf. Latin madere "be moist;" Albanian mend "suckle;" see mast (n.2)).

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for masto-



Breast; mammary gland; nipple:mastectomy.

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