rat
n.— «Meanwhile, the Stinebakers make no attempt to conceal the fact that the Thunderbird—at least to some devout worshippers of domestic vehicles—is sort of a sacrilegious Frankenstein machine. Inside the Ford body sits a Chevrolet small-block engine. The motor is known to enthusiasts as a “mouse”—big-blocks are known as “rats”—so a small rubber mouse serves as the car’s mascot. The Stinebakers also adorn the dashboard with a sign reading “Built Ford tough with Chevy stuff.”» —“Kicking’ It” by Daniel Pike State Journal-Register (Springfield, Illinois) Sept. 24, 2006. (source: Double-Tongued Dictionary)