rip syncing
Similar to, but different from, lip syncing as rip syncing is the act of actually singing words, typically at the top of one's lungs when very drunk and having little care for the actual lyrics.
Jim was hammered last night and got rip syncing with Jill the entire Boston album. Between the two of them, they knew about 40% of the lyrics and 100% of the choruses, which the yelled very loudly.