Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
fifthly is an adverb meaning "in the fifth place". It carries one recorded sense.
in the fifth place
“fifthly, we must adhere to the rules set by the local government”
Definitions, synonyms and semantic relations for fifthly come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.