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1. Without question and beyond doubt
   "it was decidedly too expensive";
   - unquestionably, emphatically, definitely, in spades, by all odds
    
2. Showing firm determination or purpose
   "she decidedly refused to look at him or speak to him";
   - resolutely
    
3. With firmness of purpose
   "'I will come along,' she said decidedly";
   - decisively, resolutely

Encyclopedia: Decidedly