/ Dictionary / Index S seism: Meaning and Definition of Find definitions for: seism Pronunciation: (sī'zum, -sum), [key] — n. an earthquake. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: seism (Thesaurus) seising seismic Related Content Daily Word Quiz: overture Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language