The Collaborative International Dictionary of English v.0.48:

Mush \Mush\, n. [Cf. Gael. mus, muss, pap, porridge, any thick
   preparation of fruit, OHG. muos; akin to AS. & OS. m[=o]s
   food, and prob, to E. meat. See Meat.]
   Meal (esp. Indian meal) boiled in water; hasty pudding;
   supawn. [U.S.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mush \Mush\, v. t. [Cf. F. moucheter to cut with small cuts.]
   To notch, cut, or indent, as cloth, with a stamp.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mush \Mush\, n. [Perh. short for mush on, a corrupt of E.
   marchons, the cry of the voyageurs and coureurs de bois to
   their dogs.]
   A march on foot, esp. across the snow with dogs; as, he had a
   long mush before him; -- also used attributively. [Colloq.,
   Alaska & Northwestern U. S.]
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Mush \Mush\, v. i. [imp. & p. p. Mushed; p. pr. & vb. n.
   Mushing.]
   To travel on foot, esp. across the snow with dogs. -- v. t.
   To cause to travel or journey. [Rare] [Colloq., Alaska &
   Northwestern U. S.]
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

mush
    n 1: any soft or soggy mass; "he pounded it to a pulp" [syn:
         pulp, mush]
    2: cornmeal boiled in water [syn: mush, cornmeal mush]
    3: writing or music that is excessively sweet and sentimental
       [syn: treacle, mush, slop, glop]
    4: a journey by dogsled
    v 1: drive (a team of dogs or a dogsled)
    2: travel with a dogsled [syn: dogsled, mush]

Moby Thesaurus II by Grady Ward, 1.0:

126 Moby Thesaurus words for "mush":
   airing, amble, bathos, bazoo, bleeding heart, breakfast food,
   butter, cataplasm, cereal, chaps, chops, cloyingness,
   constitutional, cornflakes, countenance, crush, dental pulp, dial,
   dry cereal, embouchure, face, facies, farina, favor, features,
   forced march, frumenty, gab, gob, goo, grits, gruel, hasty pudding,
   hearts-and-flowers, hike, hominy grits, hot cereal, jaunt, jaw,
   jaws, jowls, kasha, kisser, lineaments, lips, loblolly, mandibles,
   map, march, mash, maudlinness, maw, mawkishness, maxilla, millet,
   mouth, mug, mushiness, muzzle, namby-pamby, namby-pambyism,
   namby-pambyness, nostalgia, nostomania, oatmeal, oral cavity,
   oversentimentalism, oversentimentality, pan, paper pulp, parade,
   paste, peripatetic journey, peripateticism, phiz, physiognomy,
   pith, plaster, porridge, poultice, premaxilla, promenade, pudding,
   puffed rice, puffed wheat, pulp, pulp lead, pulpwood, puss,
   rag pulp, ramble, rolled oats, romanticism, row, sauce, saunter,
   schlep, sentiment, sentimentalism, sentimentality, slop,
   sloppiness, slush, smash, soap opera, sob story, sponge, squash,
   stretch, stroll, sulfate pulp, sulfite pulp, sweetness and light,
   tearjerker, traipse, tramp, trap, trudge, turn, visage, walk,
   walking tour, wheatflakes, white lead, wood pulp, yap



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

MUSH
       Multi-User Shared Hallucination (MUD)


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

MUSH

   1.  Multi-User Shared Hallucination.

   2.  Mail Users' Shell.