Semen is a sticky white or yellowish fluid that contains sperm. Semen (pronounced SEE-men or SEE-mən) is the fluid that comes out from the end of a man's penis when he has an orgasm (the height of sexual excitement) and ejaculates.emen is the fluid that comes out from the end of a man's penis when he has an orgasm (the height of sexual excitement) and ejaculates. It is usually white, but may also be slightly grey or yellow. If there is blood in the semen, it can look pink or reddish.