catflap.org Online Dictionary Query

  hollow back /hˈɒləʊ bˈak/
  hohler Rücken
     Synonyms: loose back, open back, false back
  
   see: book spine, spine of a book, spine, back of a book, shelf-back, back, backbone, book spines, spines, backs, backbones, cracked spine, tight back, flat back, square back, spring back, hand-bound book with French joints
  

  hollow back /hˈɒləʊ bˈak/
  Hohlkreuz  [med.]
        "have a hollow back"  - ein Hohlkreuz haben

  hollow back /hˈɒləʊ bˈak/
  Sprungrücken  [print]
     Synonyms: spring back, open back, loose back