Source : Webster's Revised Unabridged Dictionary (1913)

Irrigate \Ir"ri*gate\, v. t. [imp. & p. p. {Irrigated}; p. pr. &
   vb. n. {Irrigating}.] [L. irrigatus, p. p. of irrigare to
   irrigate: ir- in + rigare to water; prob. akin to E. rain.
   See {Rain}.]
   1. To water; to wet; to moisten with running or dropping
      water; to bedew.

   2. (Agric.) To water, as land, by causing a stream to flow
      upon, over, or through it, as in artificial channels.

Source : WordNet®

irrigate
     v 1: supply with water, as with channels or ditches or streams;
          "Water the fields" [syn: {water}]
     2: supply with a constant flow or sprinkling of some liquid,
        for the purpose of cooling, cleansing, or disinfecting;
        "irrigate the wound"