from The American Heritage® Dictionary of the English Language, 5th Edition.

  • adjective Subject to or causing doubt.
  • adjective Experiencing or showing doubt.
  • adjective Of uncertain outcome; undecided.
  • adjective Raising doubts as to legitimacy, honesty, or respectability; suspicious.

from The Century Dictionary.

  • Full of doubt; having doubt; not settled in opinion.
  • Causing doubt; dubious; ambiguous; uncertain; not distinct in character, meaning, or appearance; vague: as, a doubtful expression; a doubtful hue.
  • Admitting of or subject to doubt; not obvious, clear, or certain; questionable.
  • Of uncertain issue; precarious; shifting.
  • Of questionable or suspected character.
  • Fearful; apprehensive; suspicious.
  • Indicating doubt; disturbed by doubt.
  • In prosody, variable in quantity; capable of being pronounced or measured either as a long or as a short; common; dichronous.

from the GNU version of the Collaborative International Dictionary of English.

  • adjective Not settled in opinion; undetermined; wavering; hesitating in belief; also used, metaphorically, of the body when its action is affected by such a state of mind.
  • adjective Admitting of doubt; not obvious, clear, or certain; questionable; not decided; not easy to be defined, classed, or named.
  • adjective Characterized by ambiguity; dubious
  • adjective Of uncertain issue or event.
  • adjective obsolete Fearful; apprehensive; suspicious.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • adjective Subject to, or causing doubt
  • adjective Experiencing or showing doubt, sceptical
  • adjective Undecided or of uncertain outcome
  • adjective obsolete Fearsome, dreadful.
  • adjective Improbable or unlikely
  • adjective Suspicious, or of dubious character
  • adjective Unclear or unreliable

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adjective open to doubt or suspicion
  • adjective fraught with uncertainty or doubt
  • adjective unsettled in mind or opinion


from Wiktionary, Creative Commons Attribution/Share-Alike License

From doubt +‎ -ful.



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  • Etymology compared to that of dubious on that page.

    January 8, 2009