/ Dictionary / Index B biconditional: Meaning and Definition of Find definitions for: bi•con•di•tion•al Pronunciation: (bī"kun-dish'u-nl), [key] — adj. Logic. (of a proposition) asserting that the existence or occurrence of one thing or event depends on, and is dependent on, the existence or occurrence of another, as “A if and only if B.” Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. biconcave bicone Related Content Daily Word Quiz: blanch Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language