memory leak n. An error in a program's dynamic-store allocation logic that causes it to fail to reclaim discarded memory, leading to eventual collapse due to memory exhaustion. Also (esp. at CMU) called core leak. These problems were severe on older machines with small, fixed-size address spaces, and special "leak detection" tools were commonly written to root them out. With the advent of virtual memory, it is unfortunately easier to be sloppy about wasting a bit of memory (although when you run out of memory on a VM machine, it means you've got a real leak!).