Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
hollow-back is a noun meaning "an abnormal inward (forward) curvature of the vertebral column". It carries one recorded sense.
an abnormal inward (forward) curvature of the vertebral column
Definitions, synonyms and semantic relations for hollow-back come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.