I figure I'd share what I found recently at Car Blog from 99rides:

Ok well Im getting a bit of flack about calling some of the rides a donk. Here is the definition as I know it NOW..

A traditional donk is a 1970s-era car with a sloping rear end

 A "box" is a sub-type of a donk, usually a 1980s-era car with a boxy or squared-off front and rear end

A "bubble" is another sub-type and is usually a car with smooth, streamlined lines from the 1990s or 2000s. Ie 94-96 impala

 

Found at: Car Blog from 99rides