From Pornopedia, the sexy encyclopedia

Eupareunia is the state of both sexual partners having an orgasm at the same time. More commonly called mutual orgasm or mutual climax, the idea was encouraged by a scientific approach in the early 20th century and was overly emphasized as an objective and a sign of true sexual satisfaction in intimate relationships. Even within homosexual relationships, where the disparity between men and women's arousal would be accounted for, this is an unlikely state to reach easily without practise, extreme familiarity with a partner, and mutual orgasm as a specific goal.