/ Dictionary / Index M microfibril: Meaning and Definition of Find definitions for: mi•cro•fi•bril Pronunciation: (mī"krō-fī'brul, -fib'rul), [key] — n. Cell Biol. a microtubule, microfilament, or other fine threadlike structure of a cell. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. microfiber microfiche Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language