A small piece, part, or quantity of something. A unit of 12 1 / 2 cents (used only in even multiples). A mouthpiece, typically made of metal, that is attached to a bridle and used to control a horse. A tool or piece for boring or drilling, typically of metal. A unit of information expressed as either a 0 or 1 in binary notation. Put a bit into the mouth of (a horse). (of a person or animal) use the teeth to cut into something in order to eat it. (of a tool, tire, boot, etc.) grip a surface.