/ Dictionary / Index A actinic ray: Meaning and Definition of Find definitions for: actin'ic ray' Pronunciation: [key] — Physics. Physics. a ray of light of short wavelengths, as ultraviolet or violet, that produces photochemical effects. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. actinic actinide Related Content Daily Word Quiz: reclusive Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language