1. To be out of equilibrium; to not be straight, level, or aligned properly; to be in a state of chaos or confusion. I've been off-kilter ever since I got that blow to the head during football practice. The economy is still off-kilter in many countries across Europe, even as the global economy has started to recover.
2. To not be working correctly or properly; to be out of order; to be out of w(h)ack. It sounds like your car's engine is a bit off-kilter. I'd recommend taking it to a mechanic before you go for any long drives.