Source : Webster's Revised Unabridged Dictionary (1913)

Thorough \Thor"ough\, prep. [See {Through}.]
   Through. [Obs.] --Spenser. Shak.

Thorough \Thor"ough\, a.
   1. Passing through; as, thorough lights in a house. [Obs.]

   2. Passing through or to the end; hence, complete; perfect;
      as, a thorough reformation; thorough work; a thorough
      translator; a thorough poet.

Thorough \Thor"ough\, adv.
   1. Thoroughly. [Obs. or Colloq.] --Chaucer.

   2. Through. [Obs.] --Shak.

Thorough \Thor"ough\, n.
   A furrow between two ridges, to drain off the surface water.
   [Prov. Eng.] --Halliwell.

Source : WordNet®

thorough
     adj 1: painstakingly careful and accurate; "our accountant is
            thorough"; "thorough research"
     2: very thorough; exhaustively complete; "an exhaustive study";
        "made a thorough search"; "thoroughgoing research" [syn: {exhaustive},
         {thoroughgoing}]