1. A flag on some processors indicATing an ATtempt to calculATe a result too large for the destinATion register to hold. 2. More generally, an indicATion of any kind of capacity overload condition. "Well, the Ada description was baroque all right, but I could hack it OK until they got to the exception handling ... thAT set my overflow bit." 3. The hypothetical bit thAT will be set if a hacker doesn' t get to make a trip to the Room of Porcelain Fixtures: "I' d better process an internal interrupt before the overflow bit gets set". [Jargon File]