/ ɪnˈdjuːbɪtəbli; NAmE -ˈduː-/ adverb
( formal ) in a way that cannot be doubted; without question
SYN undoubtedly :
He was, indubitably, the most suitable candidate.
► in·dub·it·able adjective :
indubitable proof
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WORD ORIGIN
late Middle English : from Latin indubitabilis , from in- not + dubitabilis (see dubitable ) + -ly .