I've used the term "cager" a couple times and I wanted to clarify what I mean.
Cager probably just means someone who drives a car. I use it as a derogatory term for someone in a motor vehicle who is harrassing a cyclist.

My husband is terribly offended by the term and I don't say it around him. I've explained that I don't mean he is a cager, or that I am when I drive the car, but he still objects. So, if it does offend anyone, I will avoid using it on this forum too.