I. ˈnäk-ˌdau̇n adjective
Date: 1690
1. : having such force as to strike down or overwhelm
a bewildering assortment of knockdown arguments — J. W. Krutch
2. : that can easily be assembled or disassembled
a knockdown table
3. chiefly British : extremely low : reduced
knockdown prices
II. noun
Date: 1809
1. : the action of knocking down
2. : something (as a blow) that strikes down or overwhelms
3. : something (as a piece of furniture) that can be easily assembled or disassembled