/ Dictionary / Index T thread mark: Meaning and Definition of Find definitions for: thread' mark" Pronunciation: [key] a thin threading in paper currency to make counterfeiting difficult. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. thread-line fishing thread rope Related Content Daily Word Quiz: frugal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language