/ Dictionary / Index T theism: Meaning and Definition of Find definitions for: the•ism Pronunciation: (thē'iz-um), [key] — n. the belief in one God as the creator and ruler of the universe, without rejection of revelation (distinguished from deism). belief in the existence of a god or gods (opposed to atheism). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: theism (Thesaurus) theirself Theiss Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language