exo- WORD ORIGIN a combining form meaning “outside,” “outer,” “external,” used in the formation of compound words: exocentric.
Also. Origin of exo- Greek, combining form of éxō outside Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019 British Dictionary definitions for exo- exo- 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).
Online Etymology Dictionary, © 2010 Douglas Harper exo- in Medicine exo- pref. 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 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.