a combining form meaning “world,” “universe,” used in the formation of compound words: cosmography; in contemporary usage, sometimes representing Russian kosmo-, it may mean “outer space,” “space travel,” or “cosmic ray”: cosmonaut.
Also especially before a vowel, cosm-.
Origin of cosmo-
< Greek kosmo-, combining form of kósmos cosmos
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
before a vowel cosm-
indicating the world or universecosmology; cosmonaut; cosmography
Word Origin for cosmo-
from Greek: cosmos
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
before a vowel cosm-, word-forming element from Latinized form of Greek kosmos (see cosmos). In older use, "the world, the universe;" since 1950s, especially of outer space.
Online Etymology Dictionary, © 2010 Douglas Harper