Also found in: Medical.
1. Radial in form: actinoid.
2. Actinic radiation: actinometer.
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.
actino-or before a vowel
1. indicating a radial structure: actinomorphic.
2. indicating radioactivity or radiation: actinometer.
[from Greek aktino-, from aktis beam, ray]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
a combining form with the meaning “ray, beam,” used with the particular senses “radiation” in the physical sciences (actinometer) and “having raylike structures,” “radiate in form” in biology (actinomyces).
[< Greek, comb. form representing aktis, genitive aktînos ray, beam; see -o-]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.