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