In a way that expresses doubt, skepticism, or disbelief; done in a manner that questions or casts doubt on something.
From 'dubious' (Latin 'dubius') plus the adverbial suffix '-ly.' The adverb form allows the quality of doubt to modify verbs and other words in sentences.
The word is often used sarcastically—someone says 'dubiously, he claimed to have cleaned his room' when they clearly don't believe the claim at all.
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