1. (活动)神秘兮兮的，秘密的
    A cloak-and-dagger activity is one which involves mystery and secrecy.

cloak-and-dagger的解释

    e.g. She was released from prison in a cloak and dagger operation yesterday...
           在昨天的一次秘密行动中她从监狱获释。
    e.g. They met in classic cloak-and-dagger style beside the lake in St James''s Park.
           他们像经典间谍片里所演的那样，偷偷摸摸地在圣詹姆斯公园的湖边相会。

1. conducted with or marked by hidden aims or methods

    e.g. clandestine intelligence operations
           cloak-and-dagger activities behind enemy lines
           hole-and-corner intrigue
           secret missions
           a secret agent
           secret sales of arms
           surreptitious mobilization of troops
           an undercover investigation
           underground resistance

    Synonym: clandestinehole-and-corner(a)hugger-muggerhush-hushsecretsurreptitiousundercoverunderground