Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
lengthily is an adverb meaning "in a lengthy or prolix manner". It carries one recorded sense.
in a lengthy or prolix manner
“the argument went on lengthily”
“she talked at length about the problem”
Definitions, synonyms and semantic relations for lengthily come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. .