Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
flip-flap is an adverb meaning "with repeated strokes and noise". It carries one recorded sense.
with repeated strokes and noise
“something going flip-flap in the night”
Definitions, synonyms and semantic relations for flip-flap come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.