SURREPTITIOUS

[adjective] - done secretly, without anyone seeing or knowingShe seemed to be listening to what I was saying, but I couldn't help noticing her surreptitious glances at the clock.Through a series of surreptitious meetings with an informer, the journalists Woodward and Bernstein found out about Watergate.He'd been so surreptitious about his drinking that no one realized he'd become an alcoholic.