A phrase which, when said about a person, indicates that this person is allocating funds from some public treasury (the government, theirwork, and so forth) for their personal use. Also sometimes said as having one's "hand in the till."
Q: "How can Rod Blagojevich afford to buy that new yacht?"
A: "Oh, he was known to dip into the till quite oftenwhile he was governor of Illinois."
"Stacy got fired from her job as a bartender because she was caught with her hand in the till."