The Collaborative International Dictionary of English v.0.48:

Ferrule \Fer"rule\ (f[e^]r"r[i^]l or f[e^]r"r[.u]l; 277), 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]

The Collaborative International Dictionary of English v.0.48:

Ferule \Fer"ule\ (? or ?; 277), n. [L. ferula: cf. F. f['e]rule.
   See Ferula.]
   1. A flat piece of wood, used for striking, children, esp. on
      the hand, in punishment.
      [1913 Webster]

   2. A ferrule. [R.]
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Ferule \Fer"ule\, v. t. [imp. & p. p. Feruled; p. pr. & vb. n.
   Feruling.]
   To punish with a ferule.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ferule
    n 1: a switch (a stick or cane or flat paddle) used to punish
         children