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

THOROUGH is a 8 letter word that starts with T.

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

2. \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.
   
   

3. \Thor"ough\, adv.
   1. Thoroughly. [Obs. or Colloq.] --Chaucer.
   
   2. Through. [Obs.] --Shak.
   
   

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