万一，倘若，万分之一的概率下

1. (if) by some chance, by some possibility, in the unlikely event that, 10000 to 1

adverb (fukushi)

（极不可能发生的）紧急情况，最坏（情况）

2. (unlikely event of) emergency, the worst(-case scenario)

noun (common) (futsuumeishi)