Complacentially is a rare and complex word that refers to something done in a complacent manner. The IPA phonetic transcription of this word is /kəmpleɪˈsɛnʃəli/, which can help readers understand how to pronounce it. The initial syllable /kəm/ is followed by a stressed syllable /pleɪ/, then includes a schwa sound /ə/ in the third syllable /sɛn/, and ends with a /ʃəli/ sound at the final syllable. Despite its complexity, this word can add depth to a writer's vocabulary when used appropriately.
In an accommodating manner.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.