Similar to getting owned, 0wned, pwned, 0wn3d, pwn3d, own3d. Except your decimation has come at a complete surprise. For instance, being one-shotted from an enemy in hiding. Or turning the corner and running into 12 of your enemies. They all blast at the same time and you instantly drop. Also, a Raid Boss kill can be WTF Truck.
I was grinding away just about to level when I got wtf truck by a pos kos rival.