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