Web 上的定义很不精确。被迫加一句容易衡量的：

In the female, orgasm is preceded by moistening of the vaginal walls and enlargement of the clitoris. The clitoris moves inward under the clitoral hood. The vagina decreases in size by about a third. There are rhythmic contractions of the uterus, vagina and pelvic muscles. After orgasm, the clitoris emerges from under the clitoral hood and returns to normal size. Women do not have a refractory period during which they cannot have another orgasm.

Add:

The key is INVOLUNTARY continous muscle strong contractions in vigina.