Source : Webster's Revised Unabridged Dictionary (1913)

Tether \Teth"er\, n. [Formerly tedder, OE. tedir; akin to LG.
   tider, tier, Icel. tj[=o]?r, Dan. t["o]ir. [root]64.]
   A long rope or chain by which an animal is fastened, as to a
   stake, so that it can range or feed only within certain
   limits.

Tether \Teth"er\, v. t. [imp. & p. p. {Tethered}; p. pr. & vb.
   n. {Tethering}.]
   To confine, as an animal, with a long rope or chain, as for
   feeding within certain limits.

         And by a slender cord was tethered to a stone.
                                                  --Wordsworth.

Source : WordNet®

tether
     n : restraint consisting of a rope (or light chain) used to
         restrain an animal [syn: {leash}, {lead}]
     v : tie with a tether; "tether horses"