Orgasm is the sudden discharge of accumulated sexual tension resulting in rhythmic muscular contractions in the pelvic region that produce intensely pleasurable sensations followed by rapid relaxation. Orgasm is also in part a psychological experience of pleasure and abandon, when the mind is focused solely on the personal experience. It is sometimes called climaxing or coming.

In Masters and Johnson's original research of the human sexual response cycle, orgasm is the third of four stages, occurring after the plateau phase and before the resolution phase. Another widely accepted model of the sexual response cycle, developed by Helen Singer Kaplan, M.D., PhD., involves just three stages: desire, excitement and orgasm.

Orgasms vary from person to person and for each individual at different times. Sometimes orgasm is an explosive, amazing rush of sensations, while others are milder, subtler, and less intense. The differences in intensity of orgasms can be attributed to physical factors, such as fatigue and length of time since last orgasm, as well as to a wide range of psychosocial factors, including mood, relation to partner, activity, expectations, and feelings about the experience.

Orgasm — A Total Body Response
There are several physiological components of orgasm. First, orgasm is a total body response, not just a pelvic event. Brain wave patterns have shown distinct changes during orgasm, and muscles in many different areas of the body contract during this phase of sexual response. Some people experience the involuntary contraction of facial muscles resulting in what looks like a grimace or an expression of discomfort or displeasure, but it is actually an indication of high sexual arousal.

The most characteristic physical feature of orgasm is the sensation produced by the simultaneous rhythmic contractions of the pubococcygeus muscle (pc muscle). Along with contractions of the anal sphincter, rectum and perineum, the uterus and outer third of the vagina (the orgasmic platform) for women, and the ejaculatory ducts and muscles around the penis for men, this constitutes the reflex of orgasm.

The first few contractions are intense and close together, occurring at about 0.8-second intervals. As orgasm continues, the contractions diminish in intensity and duration and occur at less frequent intervals.

Orgasm Differences Between Men and Women
Despite the anatomical differences between male and female genitals, orgasms in men and women are physiologically and psychologically, or subjectively, very similar.