/ Dictionary / Index F filum: Meaning and Definition of Find definitions for: fi•lum Pronunciation: (fī'lum), [key] — pl. -la a threadlike structure; filament. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: filum (Thesaurus) filtrate fimble Related Content Daily Word Quiz: belligerent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language