Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
inefficaciously is an adverb meaning "in an ineffective manner". It carries one recorded sense.
in an ineffective manner
“he dealt with the problem rather ineffectively”
Definitions, synonyms and semantic relations for inefficaciously come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.