PDL (piddle or puddle) [acronym for Push Down List] n. 1. A LIFO queue (stack); more loosely, any priority queue; even more loosely, any queue. A person's pdl is the set of things he has to do in the future. One speaks of the next project to be attacked as having risen to the top of the pdl. "I'm afraid I've got real work to do, so this'll have to be pushed way down on my pdl." See PUSH and POP. 2. Dave Lebling (PDL@DM).