Brit, informal
chiefly derog a musician, esp one who plays pop music and is more concerned with technique than with content or expression
a person who has a strong interest in or vast knowledge of music, esp pop music
(used before a noun) denoting or relating to music, musicians, music enthusiasts, etc esp in the pop music world
Fiona will know who sang that – she's a real muso head
chiefly Aus, NZ, informal a musician, esp one who plays professionally
[a contraction of music or musician + -o1]