/ Dictionary / Index M myelofibrosis: Meaning and Definition of Find definitions for: my•e•lo•fi•bro•sis Pronunciation: (mī"u-lō-fī-brō'sis), [key] — n. Pathol. the replacement of bone marrow by fibrous tissue, characteristic of leukemia and certain other diseases. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: myelofibrosis (Thesaurus) myelocyte myelogenic Related Content Daily Word Quiz: vertigo Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language