alt. 'munge' /muhnj/ [in 1960 at MIT, 'Mash Until No Good'; sometime after that the derivation from the recursive acronym 'Mung Until No Good' became standard]
vt. 1. To make changes to a file, esp. large-scale and irrevocable changes. See BLT.
2. To destroy, usually accidentally, occasionally maliciously. The system only mungs things maliciously; this is a consequence of Finagle's Law. See scribble, mangle, trash, nuke. Reports from USENET suggest that the pronunciation /muhnj/ is now usual in speech, but the spelling 'mung' is still common in program comments (compare the widespread confusion over the proper spelling of kluge).
3. The kind of beans of which the sprouts are used in Chinese food. (That's their real name! Mung beans! Really!)