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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Example sentences from the Web for exo

British Dictionary definitions for exo (1 of 2)

/ (ˈɛksəʊ) /


Australian an informal word for excellent

British Dictionary definitions for exo (2 of 2)


combining form

external, outside, or beyondexobiology; exothermal

Word Origin for exo-

from Greek exō outside
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Medical definitions for exo



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

Scientific definitions for exo


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.