Also found in: Medical.
1. Radial in form: actinoid.
2. Actinic radiation: actinometer.
actino-or before a vowel
1. indicating a radial structure: actinomorphic.
2. indicating radioactivity or radiation: actinometer.
[from Greek aktino-, from aktis beam, ray]
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-]