Dictionary.com
definitions

entero-

  1. a combining form meaning “intestine,” used in the formation of compound words: enterology.
Also especially before a vowel, enter-.

Origin of entero-

< Greek, combining form of énteron intestine
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for entero-

entero-

before a vowel enter-

combining form
  1. indicating an intestineenterovirus; enteritis

Word Origin for entero-

from New Latin, from Greek enteron intestine
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 entero-

before vowels enter-, word-forming element meaning "intestine," from comb. form of Greek enteron "an intestine, piece of gut" (see enteric).

Online Etymology Dictionary, © 2010 Douglas Harper
entero- in Medicine

entero-

pref.
  1. Intestine:enteritis.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.