“Surreptitious” means sneaky, stealthy, furtive, or hidden. A child who doesn’t want to clean his room might try to hide some of the mess in a closet or under his bed, That sort of surreptitious behavior doesn’t work for long, and he’ll end up in more trouble than before – first for having a messy room, and then for trying to hide the mess.

Example:  “Joan was so surreptitious when taking extra cards that it was years before we figured out why she always won the card games.