Sec. 4D of my 2013 rulebook says (on page 42):
"For classification purposes , an automobile is a land vehicle propelled by its own means, run on at least four (45) wheels, not aligned, which shall always be in contact with the ground."
I'll assume that the words "may be aligned or. . ." can be inserted after ".wheels, "
It's clear from that. It's in the definitions pages - def. of an automobile.