The Collaborative International Dictionary of English v.0.48:

Paddock \Pad"dock\, n. [OE. padde toad, frog + -ock; akin to D.
   pad, padde, toad, Icel. & Sw. padda, Dan. padde.] (Zool.)
   A toad or frog. --Wyclif. "Loathed paddocks." --Spenser
   [1913 Webster]

   Paddock pipe (Bot.), a hollow-stemmed plant of the genus
      Equisetum, especially Equisetum limosum and the
      fruiting stems of Equisetum arvense; -- called also
      padow pipe and toad pipe. See Equisetum.

   Paddock stone. See Toadstone.

   Paddock stool (Bot.),a toadstool.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Paddock \Pad"dock\, n. [Corrupted fr. parrock. See Parrock.]
   [1913 Webster]
   1. A small inclosure or park for sporting. [Obs.]
      [1913 Webster]

   2. A small inclosure for pasture; esp., one adjoining a
      stable. --Evelyn. --Cowper.
      [1913 Webster]

   3. An enclosure used for saddling and mounting horses prior
      to a race.
      [PJC]

WordNet (r) 3.0 (2006):

paddock
    n 1: pen where racehorses are saddled and paraded before a race