A simple achievement, requiring a vehicle to smash into you while you're in armour lock. The vehicle must be going quick enough for it to explode by hitting you.
The easiest way to do this is by going into Big Team Battle and voting for Elite Slayer on Hemmorage. Elite Slayer is full of crazy vehicle (mostly ghost) action and there is plenty of opportunity to get some armour lock kills. Simply run around the middle-ish of the map and try to get the attention of some vehicles. Hopefully they'll notice you and try to splatter you. Just before they hit you, armour lock and if you're lucky they'll explode. 10 seconds later (or so..) your achievement should pop!
It's as simple as this:
(Credit to HaloBloodCookies for the video)