hot rod

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An automobile that has been rebuilt or modified to increase its speed and acceleration.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Typically a passenger vehicle modified to run and/or accelerate faster. The term may be used generically to apply to any car, truck, or motorcycle (et al.) modified for increased speed and/or performance. It may also be used to specifically describe and refer to modified cars from the original (or traditional) era of "hot rods", post World War II and prior to 1960.
• verb A colloquialism and slang term used to refer to the act of modifying a vehicle for enhanced driving performance, top speed, and/or to accelerate faster.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a car modified to increase its speed and acceleration