/ Dictionary / Index E ectostosis: Meaning and Definition of Find definitions for: ec•tos•to•sis Pronunciation: (ek"to-stō'sis, -tu-), [key] — n. the ossification of cartilage that begins under the perichondrium and proceeds inward. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ectosarc ectotherm Related Content Daily Word Quiz: blanch Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language