1.  n. a highbrow with long hair; especially a musician.  There were a few longhairs at the bar, but none of the regulars.  
2.  mod. highbrow; [of music] classical.  Longhair stuff like symphonies and art galleries bores me to tears.  
3.  n. a hippy; a long-haired youth of the 1960s. (Usually derogatory.)  There are fewer longhairs around here than there were in the sixties.