'Gymkhana' is an equestrian event. 'Motorkhana' is a derivation of the gymkhana for cars. It typically involves timed runs through a course set out with 'witches hats' or poles and can be run on dirt or a sealed surface. Some of the courses set out take their names from other types of competition, eg: straight slalom, in which a car must run a zig-zag course much as skiers do.
American Autocross is probably very similar. Autocross in Australia is more like a closed rally section, always on dirt and vehicles compete against the clock rather than other vehicles. The Confederation of Australian Motor Sport (CAMS) rules that an autocross straight should be no more than 200 metres long (218 yards).
Link to pics of MG Car Club of Victoria motorkhana at Rob Roy, East of Melbourne:
http://gallery.mgcc.info/2006RobRoyM...na2/index.html