Means being "massaged" by loud bass
music.
Often in the context of serious
car audio installations that are capable of reproducing low frequency (often 15-40hz) loud enough to shake, vibrate the listener and
car to the extent it gives the feeling of a massage.
In
sentence:
"I was out late
night driving, getting my bassage."
"
Music was so loud it bassaged me."
"That's one helluva bassage!"