The Collaborative International Dictionary of English v.0.48:

Mung \Mung\ (m[u^]ng), n. [Hind. m[=u]ng.] (Bot.)
   Green gram, a kind of legume (pulse) (Vigna radiata syn.
   Phaseolus aureus, syn. Phaseolus Mungo), grown for food
   in British India; called also gram, mung bean, Chinese
   mung bean, and green-seeded mung bean. It is an erect,
   bushy annual producing edible green or yellow seeds, and
   edible pods and young sprouts. --Balfour (Cyc. of India).
   [1913 Webster]

WordNet (r) 3.0 (2006):

mung
    n 1: erect bushy annual widely cultivated in warm regions of
         India and Indonesia and United States for forage and
         especially its edible seeds; chief source of bean sprouts
         used in Chinese cookery; sometimes placed in genus
         Phaseolus [syn: mung, mung bean, green gram, golden
         gram, Vigna radiata, Phaseolus aureus]

The Jargon File (version 4.4.7, 29 Dec 2003):

mung
 /muhng/, vt.

    [in 1960 at MIT, ?Mash Until No Good?; sometime after that the derivation
    from the recursive acronym ?Mung Until No Good? became standard; but see
    munge]

    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. In the wake of the spam epidemics of the 1990s, mung is now commonly
    used to describe the act of modifying an email address in a sig block in a
    way that human beings can readily reverse but that will fool an address
    harvester. Example: johnNOSPAMsmith@isp.net.

    4. The kind of beans the sprouts of which are used in Chinese food. (That's
    their real name! Mung beans! Really!)

    Like many early hacker terms, this one seems to have originated at TMRC;
    it was already in use there in 1958. Peter Samson (compiler of the original
    TMRC lexicon) thinks it may originally have been onomatopoeic for the sound
    of a relay spring (contact) being twanged. However, it is known that during
    the World Wars, ?mung? was U.S.: army slang for the ersatz creamed chipped
    beef better known as ?SOS?, and it seems quite likely that the word in fact
    goes back to Scots-dialect munge.

    Charles Mackay's 1874 book Lost Beauties of the English Language defined ?
    mung? as follows: ?Preterite of ming, to ming or mingle; when the
    substantive meaning of mingled food of bread, potatoes, etc. thrown to
    poultry. In America, ?mung news? is a common expression applied to false
    news, but probably having its derivation from mingled (or mung) news, in
    which the true and the false are so mixed up together that it is impossible
    to distinguish one from another.?


The Free On-line Dictionary of Computing (30 December 2018):

mung

   /muhng/ (MIT, 1960) Mash Until No Good.

   Sometime after that the derivation from the recursive
   acronym "Mung Until No Good" became standard.  1. To make
   changes to a file, especially 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!)

   Like many early hacker terms, this one seems to have
   originated at TMRC; it was already in use there in 1958.
   Peter Samson (compiler of the original TMRC lexicon) thinks it
   may originally have been onomatopoeic for the sound of a relay
   spring (contact) being twanged.  However, it is known that
   during the World Wars, "mung" was army slang for the ersatz
   creamed chipped beef better known as "SOS".

   [Jargon File]

   (1994-12-02)