underhanded

/ˌən-dər-ˈhan-dəd/

adverb

  1. underhand

adjective

  1. marked by secrecy, chicanery, and deception : not honest and aboveboard : sly

an underhanded attempt to gain power

secret covert stealthy furtive clandestine surreptitious underhanded mean done without attracting observation. secret implies concealment on any grounds for any motive. covert stresses the fact of not being open or declared.