The Acura MDX, or Honda MDX as known in Japan and Australia (only the first generation was imported), is a mid-sizeluxurycrossover SUV produced by the Japanese automaker Acura since the 2000. The MDX was the first crossover SUV to have third-row seating. The alphanumeric moniker stands for "Multi-Dimensional luxury". It was introduced as a 2001 model, replacing the slow-selling U.S.-only body-on-frameSLX, based on the Isuzu Trooper. In Japan, it filled a gap when the Honda Horizon (also based on the Trooper) was discontinued in 1999. In 2003, the Honda MDX went on sale in Japan and Australia. For 2009, Acura added a crossover to slot above the MDX, called the ZDX, similar in appearance to the BMW X6.