(FERR-tiv)

(adj.) Stealthy; surreptitious

This word is quite picturesque when you realize that "furtive" derives from Latin "fur," meaning "thief."

"He walked very slowly and circumspectly, and there was something indescribably guilty and furtive in his whole appearance."--Sir Arthur Conan Doyle, in The Hound of the Baskervilles.