To cut or kill (a person) with a blade; to slice off or lop off — often used in literary, historical, or dramatic contexts.
侍が敵を斬る場面は時代劇によく出てくる。
Scenes of a samurai cutting down an enemy often appear in period dramas.
木の枝を斬るために大きな包丁を使った。
I used a large knife to cut off the tree branch.
彼の一言で、その議題は即座に斬られてしまった（比喩的用法）。
With his one remark the topic was immediately cut off (figurative use).