/ Dictionary / Index D doubtless: Meaning and Definition of Find definitions for: doubt•less Pronunciation: (dout'lis), [key] — adv. without doubt; certainly; surely; unquestionably. probably or presumably. —adj. free from doubt or uncertainty; certain, sure. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: doubtless (Thesaurus) doubting Thomas douce Related Content Daily Word Quiz: lyceum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language