cat burglar

A thief who breaks into premises in very stealthy ways so as not to be detected, especially by climbing through upper windows, climbing across roofs, etc. The notorious cat burglar has so far robbed over a dozen homes in the area. In each case, the owners were home and had no idea someone had entered the building until the next morning. He's a huge guy, a former wrestler—you're delusional if you think you can turn him into a cat burglar. A cat burglar could sneak into your attic through this unlocked window, and you wouldn't even know!

time burglar

A person or thing that distracts or takes time from more useful or productive activities. I'm trying to catch up on work after being out sick, but my inbox is such a time burglar. I'll call my mom back later—she can be a real time burglar, and I need to finish up this essay.