The mix between a Badunkadunk and an Onion. Both of which symbolize a girl with a nice thick ass that would make a grown man cry (onion). The beauty of the word Ba-donion is that you can say it and not sound all stupid and trendy like the d-bags that can't come up with their own original sh!t.
by JRatt March 03, 2005
by JRatt July 06, 2005