/ Dictionary / Index P pyroclastic: Meaning and Definition of Find definitions for: py•ro•clas•tic Pronunciation: (pī"ru-klas'tik), [key] — adj. Geol. composed chiefly of fragments of volcanic origin, as agglomerate, tuff, and certain other rocks; volcaniclastic. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. pyrochlore pyroconductivity Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language