Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
inexpugnable is an adjective meaning "incapable of being overcome, challenged or refuted". It carries one recorded sense.
incapable of being overcome, challenged or refuted
“an impregnable argument”
“impregnable self-confidence”
Definitions, synonyms and semantic relations for inexpugnable come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.