musher

noun

1. One who drives a dogsled over ice and snow; specifically, one who participates in a dogsled race.

   “It was a record run. Each day for fourteen days they had averaged forty miles. For three days Perrault and François threw chests up and down the main street of Skaguay and were deluged with invitations to drink, while the team was the constant centre of a worshipful crowd of dog-busters and mushers.”

   “The youngest musher to enter was Dallas Seavey, who ran in the 2005 Junior Iditarod at age 17, then turned 18 one day before the Iditarod and ran that race in the same year. […] Dallas Seavey was also the youngest musher to win, taking the 2012 championship at age 25.”

   “A sled dog learns that by the time she's hungry, her musher has already prepared a meal; by the time she's tired, she has a warm bed.”

2. One who travels over snow, chiefly by dogsled but also by foot.
3. (London, slang)Synonym of mush (“a cab driver who is the owner of their cab, and sometimes a small number of other cabs as well”).

   “Nobody knew Old Joe. He was a "musher"—that is to say, he owned his own cab and mostly did night work. He gave no trouble to anybody, and came and went as a rule in the dark hours of the night.”

4. (England, dialectal)A mushroom.