/ Dictionary / Index D diactinic: Meaning and Definition of Find definitions for: di•ac•tin•ic Pronunciation: (dī"ak-tin'ik), [key] — adj. Physics. capable of transmitting actinic rays. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. diacritical diad Related Content Daily Word Quiz: penchant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language