It could mean anything from Multi-User Shared Hack, Habitat,
Holodeck, or Hallucination. to pulp. Mushing is also a general term
for traveling by dog sled.
noun
1. meal, esp. cornmeal, boiled in water or milk until it forms a
thick, soft mass, or until it is stiff enough to mold into a loaf
for slicing and frying. 2. any thick, soft mass. 3. mawkish
sentimentality or amorousness. 4. anything unpleasantly or
contemptibly lacking in coherence, force, dignity, etc.: His entire
argument was simply mush. -verb (used with object) 5. to squeeze or
crush; crunch: to mush all the candy together in a sticky ball