/ Dictionary / Index F fault line: Meaning and Definition of Find definitions for: fault' line" Pronunciation: [key] — Geol. Geol. the intersection of a fault with the surface of the earth or other plane of reference. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. faultless fault plane 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