What does "thorough" mean?

Thorough: Passing through; as, thorough lights in a house. [Obs.]

Additional senses

  1. 2.Passing through or to the end; hence, complete; perfect; as, a thorough reformation; thorough work; a thorough translator; a thorough poet.
  2. 3.Thoroughly. [Obs. or Colloq.] Chaucer.
  3. 4.Through. [Obs.] Shak.
  4. 5.A furrow between two ridges, to drain off the surface water. [Prov. Eng.] Halliwell.

Sources