SURREPTITIOUS

clandestine, cloak-and-dagger, hole-and-corner, hugger-mugger, hush-hush, secret, surreptitious, undercover, underground

(adjective) conducted with or marked by hidden aims or methods; “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”

furtive, sneak, sneaky, stealthy, surreptitious

(adjective) marked by quiet and caution and secrecy; taking pains to avoid being observed; “a furtive manner”; “a sneak attack”; “stealthy footsteps”; “a surreptitious glance at his watch”

Source: WordNet® 3.1

Etymology

Adjective

surreptitious (comparative more surreptitious, superlative most surreptitious)

Stealthy, furtive, well hidden, covert (especially movements).

Synonyms

• See covert

Source: Wiktionary

Sur`rep*ti"tious, a. Etym: [L. surreptitius, or subreptitius, fr. surripere, subripere, to snatch away, to withdraw privily; sub- under + rapere to snatch. See Sub-, and Ravish.]

Definition: Done or made by stealth, or without proper authority; made or introduced fraudulently; clandestine; stealthy; as, a surreptitious passage in an old manuscript; a surreptitious removal of goods.

– Sur`rep*ti"tious*ly, adv.

Source: Webster’s Unabridged Dictionary 1913 Edition