Definition of neck-break in English:

neck-break

Pronunciation /ˈnɛkbreɪk/

noun

rare Scottish
  • A fall in which the neck is broken; (figurative) destruction; downfall.

adjective

dialect, rare
  • Likely to break the neck; dangerous, hazardous. Compare "break-neck".

Origin

Mid 17th century (in an earlier sense). From neck + break.