1. slang A path or journey that is particularly bumpy or jarring to traverse by motor vehicle. It's just a basic dirt road that was meant for horseback riding, so it can be a bit of a kidney-buster in a jeep. The drive between towns used to be a six-hour kidney-buster on those old side roads, but now that they've put in the highway it is a very comfortable two-hour journey.
2. slang A vehicle that is very bumpy or jarring while traveling. I love this old truck, but its shock absorbers are shot, so it's quite the kidney-buster on the road. That old wooden roller coaster can be a real kidney-buster when it starts twisting around the track.
1. n. a rough ride; a rough road. This road is a kidney-buster. I wish they’d fix it.
2. n. an uncomfortable or poorly built seat in a vehicle. This kidney-buster is going to ruin my back.