DUBIOUS

doubtful, dubious

(adjective) fraught with uncertainty or doubt; “they were doubtful that the cord would hold”; “it was doubtful whether she would be admitted”; “dubious about agreeing to go”

dubious

(adjective) not convinced; “they admitted the force of my argument but remained dubious”

doubtful, dubious, dubitable, in question

(adjective) open to doubt or suspicion; “the candidate’s doubtful past”; “he has a dubious record indeed”; “what one found uncertain the other found dubious or downright false”; “it was more than dubitable whether the friend was as influential as she thought”- Karen Horney

Source: WordNet® 3.1

Etymology

Adjective

dubious (comparative more dubious, superlative most dubious)

(of a statement) Arousing doubt; questionable; open to suspicion.

(of a person) In disbelief; wavering, uncertain, or hesitating in opinion; inclined to doubt; undecided.

Usage notes

Largely synonymous with doubtful, when used of statements or facts, dubious is used when the statement is a cause of doubt, while doubtful is used when a fact is in doubt. For example, “the company’s earnings report was dubious” vs. “his chances for recovery are doubtful”.

Source: Wiktionary

Du"bi*ous, a. Etym: [L. dubius, dubiosus, fr. duo two. See Two, and cf. Doubt.]

1. Doubtful or not settled in opinion; being in doubt; wavering or fluctuating; undetermined. "Dubious policy." Sir T. Scott. A dubious, agitated state of mind. Thackeray.

2. Occasioning doubt; not clear, or obvious; equivocal; questionable; doubtful; as, a dubious answer. Wiping the dingy shirt with a still more dubious pocket handkerchief. Thackeray.

3. Of uncertain event or issue; as, in dubious battle.

Syn.

– Doubtful; doubting; unsettled; undetermined; equivocal; uncertain. Cf. Doubtful.

Source: Webster’s Unabridged Dictionary 1913 Edition