Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
feetfirst is an adverb meaning "with the feet foremost". It carries one recorded sense.
with the feet foremost
“he jumped into the pool feetfirst”
Definitions, synonyms and semantic relations for feetfirst come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.