轅門

Etymology
轅 (the shaft which connects a carriage to its horse) + 門 (gate)
 * In ancient times, when a monarch went on an expedition (ex. for hunting), the place where he stopped would be made into a camp by surrounding the location with a baricade of horse-drawn vehicles. Two of the vehicles would be upended, and their shafts would be made to meet, so as to form a makeshift gateway of sorts.

Noun

 * 1)  the entrance to a military camp
 * 2)  the outer entrance gate to a high level official's office
 * 1)  the outer entrance gate to a high level official's office