剑桥词典very unlikely to fail 万无一失的，万全的 a fail-safe plan 万无一失的计划 If something is fail-safe, it has been designed so that if one part of it does not work , the whole thing does not become dangerous . 可自动防止故障危害的；有自动保险装置的 a fail-safe device 故障保护装置 返回 fail-safe