n: The shudders, wide-eyed look, frantic little astounded noises, and eventual amazed torpor that accompanies the listening to an amazing song, usually ending in the person having a glassy-eyed look and acting in the exhausted, drained manner of someone who just had a huge orgasm
v: To exhibit the behaviors or characteristics that define the act of having a soundgasm.
Oh my lord, I was listening to my friend's MP3 player and she caught me having a soundgasm to the new rock she has on there. I was so embarassed. =]