Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
cast-off is an adjective meaning "thrown away". It carries one recorded sense.
thrown away
“wearing someone's cast-off clothes”
“throwaway children living on the streets”
“salvaged some thrown-away furniture”
Definitions, synonyms and semantic relations for cast-off come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.