Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
undefendable is an adjective meaning "not defended or capable of being defended". It carries one recorded sense.
not defended or capable of being defended
“an open city”
“open to attack”
Definitions, synonyms and semantic relations for undefendable come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.