/ Dictionary / Index S synsacrum: Meaning and Definition of Find definitions for: syn•sac•rum Pronunciation: (sin-sak'rum, -sā'krum), [key] — pl. -sac•ra a dorsal ridge of bone in the pelvic region of birds, formed by the fusion of certain thoracic, lumbar, sacral, and caudal vertebrae. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. synovitis synsepalous Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language