1.A military term used to describe the operational condition of a piece of equipment. It means the equipment in question is NMC or is broken down. Equipment can be deadlined for safety reasons such as fuel leaks, inop headlights, Missing seatbelts, etc.
2.To have an injured body part limiting your ability to perform certain actions.
1.I can't get a dispatch for my truck, the fucking headlights are inop.
Looks like we're not going anywhere today, my panzer is throwing fuel everywhere, run over to the CPand tell the XO we're saftey deadlined.
2. No freq hopping for me this weekend, My main gun is deadlined from that girl last week.