archi- or arch-pref.1. Chief; highest; most important: archiepiscopal.2. Earlier; primitive: archenteron.[French archi- and Italian arci-, both from Latin archi-, from Greek arkhi-, arkh-, from arkhein, to begin, rule.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.archi- combining form a variant of arch- Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014archi- a combining form with the general sense ?first, principal,? prefixed to nouns denoting things that are earliest, most basic, or bottommost (archiblast; archiphoneme; architrave); or denoting individuals who direct or have authority over others of their class, usu. named by the base noun (archimandrite; architect). Also, esp. before a vowel,arch-. Compare arch-1, arche-.[