a combining form meaning “outer,” “outside,” “external,” used in the formation of compound words: ectoderm.
Also especially before a vowel, ect-.

Origin of ecto-

combining form of Greek ektós outside Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for ecto-


combining form

indicating outer, outside, externalectoplasm

Word Origin for ecto-

from Greek ektos outside, from ek, ex out
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

Medicine definitions for ecto-



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