Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Fraught with uncertainty or doubt; undecided.
  • adj. Arousing doubt; doubtful: a dubious distinction.
  • adj. Of questionable character: dubious profits.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. Arousing doubt; questionable; open to suspicion.
  • adj. In disbelief; wavering, uncertain, or hesitating in opinion; inclined to doubt; undecided.

from the GNU version of the Collaborative International Dictionary of English

  • adj. Doubtful or not settled in opinion; being in doubt; wavering or fluctuating; undetermined.
  • adj. Occasioning doubt; not clear, or obvious; equivocal; questionable; doubtful.
  • adj. Of uncertain event or issue.

from The Century Dictionary and Cyclopedia

  • Doubting; hesitating; wavering or fluctuating in opinion, but inclined to doubt.
  • Doubtful; marked by or occasioning doubt or uncertainty; difficult to determine or relieve of uncertainty; not distinct or plain; puzzling: as, a dubious question; a dubious light.
  • Of uncertain event or issue: as, a dubious undertaking.
  • Liable to doubt or suspicion; of doubtful quality or propriety; questionable: as, a man of dubious character; a dubious transaction; his morals or his methods are dubious. Synonyms Unsettled, undetermined.
  • Doubtful, Ambiguous, etc. (see obscure, a.); questionable, problematical, puzzling.

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

  • adj. open to doubt or suspicion
  • adj. fraught with uncertainty or doubt
  • adj. not convinced

Etymologies

From Latin dubius; see dwo- in Indo-European roots.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin dubius. (Wiktionary)

Examples

Comments

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  • And the Latin root dub- is probably from a contraction of du- "two" + hab- "have", i.e. "be in two minds".

    January 8, 2009

  • OED etymology of dubious is:
    ad. L. dubis-us doubtful, f. dubium doubt, neuter of dubius doubtful.

    Etymology of doubtful as a noun is:
    ME. a. Of. dute, dote, doute, vbl. n. f. douter to DOUBT. The spelling doute, dought, arose from the spoken identity, which per contra caused DOUGHTY to be spelt doubty. As to the mod. spelling with b, see DOUBT v.

    As a verb is:
    ME. duten, douten, a. OF. duter, doter, douter, (14-16th c. also doubter):L. dubitre to waver in opinion, hesitate, related to dubius wavering to and fro, DUBIOUS. The normal 14th c. forms in Fr. and Eng. were douter, doute; the influence of Latin caused these to be artificially spelt doubt-, which in 17th c. was again abandoned in Fr., but retained in Eng.
    Branch II ‘to fear, to be in fear’, a development of the verb in OF., was an early and very prominent sense of the vb. and its derivatives in ME.: cf. also REDOUBT, etc

    Doesn't look like any of them come from Gaelic.

    January 8, 2009

  • Irish dubh dark, black. Hence, doubtful?

    January 8, 2009