Style of music that originally was for people to dance to, feel good music rebelling against the austere old classical style. Eventually a bunch of bitter hipsters turned it into an expression of elitism, and it lost major popularity outside "intellectuals" and conservatories. When it was institutionalized, and every suburban white boy could be the next coltrane, it became as calculated and elitist as the classical music it was supposed to rebel against. True jazz stirs both thoughts and emotions (and can be, *gasp* FUN), don't mistake anything else for it.
"oh my god, that Jazz song is in 17/4 timing-- it must be good" - overheard at many a concert
"Thelonious Monk is incredible, complex when he wants to be, simple when he wants to be, unconventional yet always putting the mood first" - me