/ Dictionary / Index P pneumonoultramicroscopicsilicovolcanoconiosis: Meaning and Definition of Find definitions for: pneu•mo•no•ul•tra•mi•cro•scop•ic•sil•i•co•vol•ca•no•co•ni•o•sis Pronunciation: (n'mu-nō-ul"tru-mī"kru-skop"ik-sil'i-kō"vol-kā"nō-kō"nē-ō'sis, ny'-), [key] — n. an obscure term ostensibly referring to a lung disease caused by silica dust, sometimes cited as one of the longest words in the English language. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. pneumonoconiosis pneumothorax Related Content Daily Word Quiz: sylvan Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language