Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
disadvantageously is an adverb meaning "in a disadvantageous way; to someone's disadvantage". It carries one recorded sense.
in a disadvantageous way; to someone's disadvantage
“the venture turned out badly for the investors”
“angry that the case was settled disadvantageously for them”
Definitions, synonyms and semantic relations for disadvantageously come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.