[thor.ough] prep [ME thorow, fr. OE thurh, thuruh, prep. & adv.] (bef. 12c) archaic: through
[2]thorough adv (bef. 12c) archaic: through [3]thorough adj (15c) 1: carried through to completion: exhaustive "a ~ search"
2. a: marked by full detail "a ~ description" b: careful about detail: painstaking "a ~ scholar" c: complete in all respects "~ pleasure" d: having full mastery (as of an art) "a ~ musician"
3: passing through -- thor.ough.ly adv -- thor.ough.ness n