indecisively has no recorded synonym. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is decisively.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
lacking firmness or resoluteness
“`I don't know,' he said indecisively”
without finality; inconclusively
“the battle ended indecisively; neither side had clearly won but neither side admitted defeat”
Synonyms, antonyms and the broader and narrower relations for indecisively come from Princeton University’s WordNet. Full sources and licences.