1
general::
Phrase(s): mow someone or something down
to cut, knock, or shoot someone or something down. • The speeding car almost mowed us down. • The car mowed down the pedestrian.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
1. Destroy in great numbers, especially in battle, as in The machine gun mowed them down as they advanced. [Late 1500s] 2. Overwhelm, as in He mowed down the opposition with his arguments. This usage, like the first, alludes to mowing, the cutting of grass with a scythe or other implement.
American Heritage Idioms