<p><strong>Noun</strong></p><ul><li>Machinery: a removable drilling or boring tool for use in a brace, drill press, or the like.</li><li>a removable boring head used on certain kinds of drills, as a rock drill.</li><li>a device for drilling oil wells or the like, consisting of a horizontally rotating blade or an assembly of rotating toothed wheels.</li><li>the mouthpiece of a bridle, having fittings at each end to which the reins are fastened.</li><li>anything that curbs or restrains.</li><li>the blade or iron of a carpenter's plane.</li><li>the cutting part of an ax or hatchet.</li><li>the wide portion at the end of an ordinary key that moves the bolt.</li></ul>