from The American Heritage® Dictionary of the English Language, 4th Edition
- Outside; external: exoskeleton.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- outside, external
from the GNU version of the Collaborative International Dictionary of English
- A prefix signifying out of, outside.
from The Century Dictionary and Cyclopedia
- n. A prefix in words of Greek origin, meaning ‘without,’ ‘outside’: used chiefly in scientific compounds, where it is usually equivalent to ecto-: opposed to endo- or onto-.
From Greek exō, outside, from ex, out of; see eghs in Indo-European roots.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Ancient Greek ἔξω (exō, "outer, external"). (Wiktionary)