four-by-four
noun [ C ] uk/ˌfɔː.baɪˈfɔːr/ us/ˌfɔːr.baɪˈfɔːr/ (written abbreviation 4x4)
（车辆的）四轮驱动
a vehicle whose engine supplies power to all four wheels instead of the usual two, so that it can travel easily over difficult ground
See also: four-wheel drive noun