/ Dictionary / Index S sorus: Meaning and Definition of Find definitions for: so•rus Pronunciation: (sôr'us, sōr'-), [key] — pl. so•ri one of the clusters of sporangia on the back of the fronds of ferns. See diag. under a soruslike spore mass of certain fungi and lichens. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: sorus (Thesaurus) sortition SOS Related Content Daily Word Quiz: effervescent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language