Definition from Wiktionary, the free dictionary
fail-secure (not comparable)
- A device which, if (or when) it fails, does so in a way that will cause no harm or at least a minimum of harm to other devices or danger to personnel, and doesn't cause the system to be insecure.
The primary use of the term is with regards to security doors and motorized gates. A motor that has "fail-secure" capabilities will, in case of a power outage, be able to be opened by means of a supplied hand crank.