surreptitious

Meanings

• marked by quiet and caution and secrecy; taking pains to avoid being observed;
• "a surreptitious glance at his watch"
• conducted with or marked by hidden aims or methods;
• "surreptitious mobilization of troops"

Synonyms

• furtive
• sneak
• sneaky
• stealthy
• clandestine
• cloak-and-dagger
• hole-and-corner
• hugger-mugger
• hush-hush
• secret
• undercover
• underground

surreptitious is not valid in Words With Friends