Definition of "collet"

A band, flange, ferrule, or collar, designed to grip and hold a tool or a workpiece under proper control, and usually to release it under control thereafter; such a collet usually is made of a hard, springy material, especially a metal.  examples

(jewelry) The rim (of a ring) within which a jewel is set.  examples

(horticulture) In an embryonic plant, the transition zone between the root and the hypocotyl (not clearly distinguishable in most plants.)  examples

Alternative form of colet (“lower servant in a church”).  examples