Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
forty-niner is a noun meaning "a miner who took part in the California gold rush in 1849". It carries one recorded sense.
a miner who took part in the California gold rush in 1849
Definitions, synonyms and semantic relations for forty-niner come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.