Knockdown

a.
  1. Of force sufficient to fell or completely overthrow; as, a knockdown blow; a knockdown argument..
  2. Designating a rivet end to be formed into a head by upsetting in fastening.
  3. Of or pertaining to the act of knocking down at an auction; specif., designating the price below which an article will not be disposed by the auctioneer.
  4. Made or constructed so as to be capable of being knocked down or taken apart, as for transportation.