1. A factory test designed to catch systems with marginal components before they get out the door the theory is that burn-in will protect customers by outwaiting the steepest part of the bathtub curve (see infant mortality). 2. A PERiod of indeterminate length in which a PERson using a computer is so intensely involved in his project that he forgets basic needs such as food, drink, sleep, etc. Warning: Excessive burn-in can lead to burn-out. See hack mode, larval stage. [Jargon File]