Merriam-Webster's Collegiate® Dictionary, 11th Edition
MUSH
I. noun
Etymology: probably alteration of mash
Date: 1671
a thick porridge made with cornmeal boiled in water or milk, something soft and spongy or shapeless,
3. weak sentimentality ; drivel , mawkish amorousness,
II. verb
Date: circa 1781
transitive verb to reduce to a crumbly mass, intransitive verb to fly in a partly or nearly stalled condition, musher noun
III. intransitive verb see: march
Date: 1897
to travel especially over snow with a sled drawn by dogs, musher noun
IV. noun
Date: 1902
a trip especially across snow with a dog team