collet

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A cone-shaped sleeve used for holding circular or rodlike pieces in a lathe or other machine.
• noun A metal collar used in watchmaking to join one end of a balance spring to the balance staff.
• noun A circular flange or rim, as in a ring, into which a gem is set.

from The Century Dictionary.

• noun See colet.
• To set in or as in a collet.
• noun A band or collar; specifically, a small collar or band worn by the inferior clergy of the Roman Catholic Church.
• noun Among jewelers: Same as culet.
• noun The ring or flange within which a jewel or a group of jewels is set, as that part of a ring which holds the seal. The word is most common in connection with large compositions of jewelers' work.
• noun In glass manufacturing, that part of a glass vessel which adheres to the pontee or iron instrument used in taking the substance from the melting-pot.
• noun In machinery, a small band of metal, as the ring which fastens the packing of a piston.
• noun In gunnery, that part of the muzzle of a cannon which lies between the astragal and the face of the piece.
• noun Same as colewort.

from the GNU version of the Collaborative International Dictionary of English.

• noun A small collar or neckband.
• noun (Mech.) A small metal ring; a small collar fastened on an arbor; ; a small socket on a stem, for holding a drill.
• noun The part of a ring containing the bezel in which the stone is set.
• noun The flat table at the base of a brilliant. See Illust. of Brilliant.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A band, flange, ferrule, or collar, usually of a hard material, especially a metal.
• noun In particular, the rim (of a ring) within which a jewel is set. Compare bezel.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a metal cap or band placed on a wooden pole to prevent splitting
• noun a band or collar that holds an individual stone in a jewelry setting
• noun a cone-shaped chuck used for holding cylindrical pieces in a lathe