"A lover of sound"
However as most people are lovers of music etc, the term audiophile points to people who love high end audio equipment and can distinguish between good speakers and bad ones, which cables to use, and can tell what bitrate an mp3 file is at... etc etc etc.
Audiophiles usually argue to the death as to which setup is best
'those monitors sound muddy as all hell'
"what? how can you tell good sir? I hear nothing wrong!"
'cuz i'm an audiophile you filthy monkey!'