/ Dictionary / Index A auxin: Meaning and Definition of Find definitions for: aux•in Pronunciation: (ôk'sin), [key] — n. Biochem. a class of substances that in minute amounts regulate or modify the growth of plants, esp. root formation, bud growth, and fruit and leaf drop. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: auxin (Thesaurus) auxilytic Auxo Related Content Daily Word Quiz: exemplary Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language