/ Dictionary / Index D diffusivity: Meaning and Definition of Find definitions for: dif•fu•siv•i•ty Pronunciation: (dif"yoo-siv'i-tē), [key] — n. Physics. the property of a substance indicative of the rate at which a thermal disturbance, as a rise in temperature, will be transmitted through the substance. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. diffusive diffusor Related Content Daily Word Quiz: effervescent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language