/ Dictionary / Index P pneumatocyst: Meaning and Definition of Find definitions for: pneu•mat•o•cyst Pronunciation: (noo-mat'u-sist, nyoo-, n'mu-tu-, ny'), [key] — n. Biol. the cavity of a pneumatophore. pneumatophore. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. pneumato- pneumatograph Related Content Daily Word Quiz: cygnet Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language