a combining form meaning “outside,” “outer,” “external,” used in the formation of compound words: exocentric.

Also ex-.

Origin of exo-

< Greek, combining form of éxō outside
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Examples from the Web for exo

Contemporary Examples of exo

Historical Examples of exo

  • She ran off to her typewriter, and in twelve minutes came back with the jingle, I'm glad I'm not an Exo.

    Facts in Jingles

    Winifred Sackville Stoner

British Dictionary definitions for exo



Australian an informal word for excellent


combining form

external, outside, or beyondexobiology; exothermal

Word Origin for exo-

from Greek exō outside
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 exo


word-forming element used in scientific words (e.g. exoskeleton), from Greek exo "outside," related to ex "out of" (see ex-).

Online Etymology Dictionary, © 2010 Douglas Harper

exo in Medicine



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

exo in Science


A prefix that means “outside” or “external,” as in exoskeleton.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.