safety nut

1. How safety, develop efficiently the petroleum resources is a hard nut to crack to put in the petroleum industry in front.
   如何安全、高效地开发石油资源是摆在石油工业面前的一道难题。
2. I was a safety nut.
   我是一位安全迷。
3. Safety Design of Leading Screw and Nut Mechanism of Vehicle Lift
   汽车举升机丝杆螺母机构的安全设计

noun

1. supplementary nut that is screwed down on a primary nut to prevent it from loosening

   Synonym:    locknut