/ Dictionary / Index S splenius: Meaning and Definition of Find definitions for: sple•ni•us Pronunciation: (splē'nē-us), [key] — pl. -ni•i a broad muscle on each side of the back of the neck and the upper part of the thoracic region, the action of which draws the head backward and assists in turning it to one side. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: splenius (Thesaurus) splenic spleno- Related Content Daily Word Quiz: neologism Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language