quad
n.— «Jam skating—a mix of break dancing, hip-hop dancing and gymnastics—has sales of four-wheeled roller skates soaring. Sales of quads, as they’re known, are up 150 percent from last year.» —“Jam on a roll” by John Tanasychuk Sun-Sentinel (Ft. Lauderdale, Florida) July 9, 2005. (source: Double-Tongued Dictionary)