from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A small, durable, general-purpose motor vehicle with four-wheel drive and a quarter-ton capacity, used by the U.S. Army during and after World War II.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A small, blocky, military-style vehicle with four-wheel drive, suited to rough terrain
Probably pronunciation of the letters GP, designation for this vehicle in the manufacturer's parts numbering system : G(overnment) + P, designator for 80-inch wheelbase reconnaissance car.(American Heritage® Dictionary of the English Language, Fourth Edition)
Probably an alteration of G.P., standing for "general purpose" (the manufacturer's designation for the vehicle). (Wiktionary)