A device designed to prevent injury or accidents(noun)
WordNet. Princeton University. 2010.
Use "safety device" in a sentence
""When a spaceship goes down to the Jovian surface, it's a radio-controlled job; it leaks like a sieve, to equalize pressure, but otherwise it's the sturdiest, most utterly powerful model ever designed; it's loaded with every instrument, every servomechanism, every safety device the human mind has yet thought up to protect a million-dollar hunk of precision equipment."