Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
unpardonably is an adverb meaning "in an unpardonable manner or to an unpardonable degree". It carries one recorded sense.
in an unpardonable manner or to an unpardonable degree
“he was inexcusably cruel to his wife”
Definitions, synonyms and semantic relations for unpardonably come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.