fail safe vs fail-safe

fail safe

fail-safe

verb
  • To compensate automatically, in the event of a failure. 

  • To make a device or mechanism fail-safe, or to add a fail-safe device or mechanism to an existing system. 

noun
  • A device, mechanism or measure designed to make something fail-safe. 

adj
  • That does not cause undue damage in the event of failure. 

  • Designed to shut off for safety if an emergency occurs. 

How often have the words fail safe and fail-safe occurred in a corpus of books? (source: Google Ngram Viewer )