From The Collaborative International Dictionary of English v.0.48 [gcide]:
Surreptitious \Sur`rep*ti"tious\, a. [L. surreptitius, or
subreptitius, fr. surripere, subripere, to snatch away, to
withdraw privily; sub- under + rapere to snatch. See Sub-,
and Ravish.]
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.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
surreptitious
adj 1: 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" [syn: furtive, {sneak(a)}, sneaky,
stealthy, surreptitious]
2: 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" [syn: clandestine,
cloak-and-dagger, {hole-and-corner(a)}, hugger-mugger,
hush-hush, secret, surreptitious, undercover,
underground]