The sound it makes.
Everyone's got a different definition of rice. The definition has changed, due to the "import scene" carrying over to a lot of domestic built cars (and European). Really, the word should have changed. Rice (cars) are rice because they come from Japan, (or any of the Asian automakers, really). I think there's a difference between "rice" and "ricey".
Rice isn't rice because it makes "a lot of noise and goes nowhere." Rice is rice because it's ugly. Audibly ugly, visually ugly, ugly because it has a small little girly engine with a small little girly block and small little girly cylinders....... what? Who cares if it's fast? You can respect them, if you want, but it's still rice.