The word "arch" typically refers to a curved structure that supports weight and spans an open space. It is commonly used in architecture to create strong and elegant structures like bridges and doorways. Full definition
An added benefit of these types of lowering springs is that they decrease the wheel arch wheel gap and in theory cuts through the wind easier given the cars lower stance. (bmwblog.com)
The narrow headlights reach almost into the wheel arches of the front fenders. (mercedesblog.com)
A further line extends upwards from the rear wheel arch in a sweeping curve. (ausmotive.com)