Curb

Curb (fr. French courber, and Lat. curvus), that which is bent, or that which bends, turns, restrains or limits. In driving or riding the curb is a chain passing from the cheek-pieces of a horse's bit beneath his lower jaw, and capable of bringing a powerful leverage to bear upon the jaw. The curb of a well is the stone casing which prevents its falling in, and the curb of a street is the edging that demarcates the street from the pavement. The word is largely used in metaphor.