A four-character idiom meaning a single warrior/person worthy of a thousand — used to praise someone extremely strong or outstanding in ability.
このチームには一騎当千のエースがいる。
This team has an ace who is a match for a thousand.
戦国時代の武将の中には一騎当千と評される者が多い。
Among the warlords of the Sengoku period, many were praised as one-man armies.
彼女は剣道部で一騎当千の強さを見せた。
She showed one-against-a-thousand strength in the kendo club.