ferrule

n. [ Formerly verrel, F. virole, fr. L. viriola little bracelet, dim. of viriae, pl., bracelets; prob. akin to viere to twist, weave, and E. withe. The spelling with f is due to confusion with L. ferrum iron. ] [ Sometimes spelled ferule. ] 1. A ring or cap of metal put round a cane, tool, handle, or other similar object, to strengthen it, or prevent splitting and wearing. [ 1913 Webster ]

2. (Machinery) Any of various circular or cylindrical metal objects used at joints in a tube, pipe, or rod, especially to assist making a tight seal at a joint. [ PJC ]

3. Hence: (Steam Boilers) A bushing for expanding the end of a flue to fasten it tightly in the tube plate, or for partly filling up its mouth. [ 1913 Webster ]

4. Hence: (Chemistry) A bushing used at the joints of metal tubing in HPLC equipment to make a tight seal. [ PJC ]

5. (Fishing) One of several small rings at the top of a casting rod which holds the fishing line. RHUD [ PJC ]