/ Dictionary / Index S substantialism: Meaning and Definition of Find definitions for: sub•stan•tial•ism Pronunciation: (sub-stan'shu-liz"um), [key] — n. Philos. the doctrine that substantial noumena exist as a basis for phenomena. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. substantial substantia nigra Related Content Daily Word Quiz: endear Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language