Source : Webster's Revised Unabridged Dictionary (1913)

Lariat \Lar"i*at\, v. t. [imp. & p. p. {Lariated}; p. pr. & vb.
   n. {Lariating}.]
   To secure with a lariat fastened to a stake, as a horse or
   mule for grazing; also, to lasso or catch with a lariat.
   [Western U.S.]

Lariat \Lar"i*at\, n. [Sp. la reata the rope; la the + reata
   rope. Cf. {Reata}.]
   A long, slender rope made of hemp or strips of hide, esp. one
   with a noose; -- used as a lasso for catching cattle, horses,
   etc., and for picketing a horse so that he can graze without
   wandering. [Mexico & Western U.S.]

Source : WordNet®

lariat
     n : a long noosed rope used to catch animals [syn: {lasso}, {riata},
          {reata}]