noun
plan B; alternative plan; workaround
A fallback or second-best plan when the ideal option is unavailable. Often used in problem-solving or strategy contexts.
当初の案が通らなかったので、次善策を検討する。
Since the original proposal didn't pass, we'll consider a plan B.
システム障害に備えて次善策を用意しておく。
We prepare a workaround in case of system failure.
最善策 is the best possible plan, the direct opposite of 次善策.
Compound of 次 (next, second) + 善 (good) + 策 (plan, measure). The exact historical derivation is uncertain, but the meaning is transparent from its components.