Definition

(Adjective) Taken, obtained, used, done, etc. by stealth, secretly, or “on the sly”; secret and unauthorized; clandestine.

In Context

“Nixon acknowledged in a statement issued May 22 that the plan contained a provision for surreptitious entry by federal agents but said he rescinded his approval of the plan five days after ordering it put into operation.”

“Nixon Approval for ‘Illegal’ Snoop Plan,” The Cedar Rapids Gazette, June 7, 1973.