Listen, just use your imagination ... lets just say there is a comparison between the contortions made by your face in the final throes of passion and the look you would have if you were drinking large amounts of vinegar...... Comprendi?
Yah is okay! - Specifically for a male - next time thou est about to orgasm ...? i.e. in the last few strokes of your task - take a photo of your screwed-up face (i.e. the one with your tongue hanging out) and you may ask - "have I just tasted vinegar"? - Now, if your still confused, I think you are a virgin....