Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
impuissance is a noun meaning "powerlessness revealed by an inability to act". It carries one recorded sense.
powerlessness revealed by an inability to act
“in spite of their weakness the group remains active”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for impuissance come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.