Dubious is the raised eyebrow. If you are dubious about something, you are not convinced — the figures do not add up and your face says so before you do. A dubious look, a dubious pause, a dubious hmm.
The trap is that dubious points both ways. A person can be dubious, meaning full of doubt, and a thing can be dubious, meaning it deserves doubt: a dubious claim, a dubious character, meat of dubious origin. It also does dry sarcasm in a few set phrases — the dubious honour of going first, the dubious pleasure of a five-hour meeting — where there is no honour and no pleasure. With people the pattern is dubious about: I am dubious about his chances. Doubtful is the mild version of the word; dubious carries suspicion, a feeling that something is not quite honest.
1adjectivedubiousNot convinced; full of doubt about something.
“He looked dubious when I said the train would be on time.”
synonyms: unconvinced, sceptical
2adjectivequestionableDeserving doubt; probably not honest, safe or good.
“The car came with a dubious service history.”
synonyms: questionable, suspect
Also accepted in games: questionable
Dubious comes from Latin dubius, and behind that stands duo, two — the same two as in English two. To be dubious is to be stuck between two options: yes or no, true or false. English doubt grew from the same Latin soil, which is why the two words feel like cousins.
Proto-Indo-European
*gʰeh₁bʰ-
Latin
dubius
English, today
dubious
Borrowed from Latin dubius. From Latin dubius; like doubt, from Latin duo (cognate to English two), implying “two alternatives” (yes or no, true or false, etc.).
Etymology from Wiktionary, CC BY-SA