Definition from Wiktionary, the free dictionary
Based on NASCAR teams' experience in the early 1950s in the legendary Carerra Panamerica, where the long hills would have otherwise overrevved the engines.
- (US, slang) The neutral gear when used while a vehicle is moving, especially when it is used to save fuel or to coast downhill faster than a vehicle can go in gear. (This is illegal in some places.)
- He shifted his car out of gear, at the top of the hill, and coasted down in Mexican overdrive.
- Playboy Magazine once answered a reader's question about the meaning of this term.