fur·tive 
(fûrtĭv)
(fûrtĭv)adj.
Characterized by, acting with, or suggesting stealth or a desire to avoid discovery; surreptitious: "J.W. from time to time gave her a furtive squeeze of the hand, but they never got to go out alone any more" (John Dos Passos). See Synonyms at secret.
[French furtif, from Old French, from Latin fūrtīvus, from fūrtum, theft, from fūr, thief; see bher-1 in the Appendix of Indo-European roots.]
furtive·ly adv.
furtive·ness n.