curb

n. 1. That which curbs, restrains, or subdues; a check or hindrance; esp., a chain or strap attached to the upper part of the branches of a bit, and capable of being drawn tightly against the lower jaw of the horse. [ 1913 Webster ]

He that before ran in the pastures wild
Felt the stiff curb control his angry jaws. Drayton. [ 1913 Webster ]

By these men, religion, that should be
The curb, is made the spur of tyranny. Denham. [ 1913 Webster ]

2. (Arch.) An assemblage of three or more pieces of timber, or a metal member, forming a frame around an opening, and serving to maintain the integrity of that opening; also, a ring of stone serving a similar purpose, as at the eye of a dome. [ 1913 Webster ]

3. A frame or wall round the mouth of a well; also, a frame within a well to prevent the earth caving in. [ 1913 Webster ]

4. A curbstone. [ 1913 Webster ]

5. (Far.) A swelling on the back part of the hind leg of a horse, just behind the lowest part of the hock joint, generally causing lameness. James Law. [ 1913 Webster ]

Curb bit, a stiff bit having branches by which a leverage is obtained upon the jaws of horse. Knight. --
Curb pins (Horology), the pins on the regulator which restrain the hairspring. --
Curb plate (Arch.), a plate serving the purpose of a curb. --
Deck curb. See under Deck. [ 1913 Webster ]