/ Dictionary / Index P proestrus: Meaning and Definition of Find definitions for: pro•es•trus Pronunciation: (prō-es'trus), [key] — n. the period immediately preceding estrus. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. proenzyme prof Related Content Daily Word Quiz: opulent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language