The first movement of the Kundalini is to make you lose your sense of body identificatiion, and that is exactly what happens in orgasm. You are flowing out of yourself as the seed and you lose all your tensions.
The word orgasm is used in Tantra in the broader context as losing all your tensions. If you are worried, losing your worry is an orgasm.

There was one fellow who used to wear shoes three times under size. He used to walk with those shoesall day long. And he used to have excruciating pain throughout the day. And people asked him, "Why do you wear those undersized shoes and bear the pain?" He said, "There is only one happiness left in my life and that is when I remove this shoe from my foot, only then I feel extremely happy. "

We are all wearing this undersize shoe, called this body, and once you find the release from this body you find happiness, the only happiness that we know, and that is called an orgasm. We want repetion of that happiness because we want to be permanently in that state. The only way to achieve that is to recognize whenever there is stress developing, and to be let go of that stress.

This is the main point of Tantra. Try to be in a state of constant orgasm, to be in the perpetual union between Siva and Shakti.

 Sri Amritanandanatha Saraswathi