1. In an exhaustive manner
   "we searched the files thoroughly"
   - exhaustively 
2. Completely and absolutely ('good' is sometimes used informally for 'thoroughly')
   - soundly, good

See also: thorough

• Klimt
• Kline
• Klinefelter
• Klinefelter syndrome
• Klinefelter's syndrome
• klipspringer
• klondike
• kloof
• Klopstock
• Klorvess
• Klotho
• kludge
• klutz
• klutzy
• Kluxer
• klystron
• Klyuchevskaya
• km
• km/h
• knack
• knacker
• knackered
• knackers
• knackwurst
• knag