- 1(literary) important as a sign or warning of something that is going to happen in the future, especially when it is something unpleasant a portentous sign
- 2(formal) (disapproving) very serious and intended to impress people synonym pompous a portentous remark
adverb She frowned portentously to add weight to her suggestion.
noun [uncountable]See portentous in the Oxford Advanced Learner's Dictionary
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