/ Dictionary / Index I in vitro: Meaning and Definition of Find definitions for: in vi•tro Pronunciation: (in vē'trō), [key] (of a biological process) made to occur in a laboratory vessel or other controlled experimental environment rather than within a living organism or natural setting. Cf. in vivo. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. inviting in vitro fertilization Related Content Daily Word Quiz: acquiesce Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language