desperate measure; last resort
A plan or action taken when one is cornered and has no other choice. Often used in formal or written contexts.
His quitting the company was a desperate measure.
The price cut is nothing more than a last resort.
From 窮余 (being driven into a corner) + の + 策 (plan, measure). The exact historical derivation is uncertain, but the phrase is conventionally associated with the idea of a last resort.