/ Dictionary / Index S serosa: Meaning and Definition of Find definitions for: se•ro•sa Pronunciation: (si-rō'su, -zu), [key] — pl. -sas, -sae the chorion. a similar membrane in insects and other lower invertebrates. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: serosa (Thesaurus) seroreaction serositis Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language