A male orgasm refers to the peak of sexual pleasure. It causes a number of physiological reactions in the male body, including rhytmic contractions of the muscles of the penis and an increase in heart rate, blood pressure, and respiration. Ejaculation often occurs in conjunction with orgasm, but not always.
More About Male Orgasm
As noted above, it's possible for men to orgasm without ejaculating. This occurs most often in adolescent boys. In addition, some men do not ejaculate until several seconds after orgasm, or have an orgasm without ejaculating at all.
It is believed that the duration of the male orgasm is shorter than women's. Women can also have a second orgasm more quickly. Studies by Alfred Kinsey in the 1950s found that up to 20% of men (compared to 14% of women) reported multiple orgasm, but now it's believed that this phenomenon is more common in women.