How would you describe an orgasm (male or female) if you had to write it for an erotica class?

Someone just asked a question about the science of orgasm. At first, I thought it was more than that, but it turned out to be a question for Wikipedia. I thought a question about the feelings that really delved deeply into the experience through time—of the whole body—might be more interesting. I wanted to challenge people to take this seriously (except blondesjon), and work hard to make everyone else feel what it’s like to be in your body. If you imagine it inside your head, and you pay attention to as many details as you can—what is happening in various parts of your body; what is happening inside your head—what would you write?