the thick white fluid containing spermatozoa that is ejaculated by the male genital tract. AKA sperm or semen. Basically when you have sex or any kind of sexual intercourse the guy will cum, that's why you always use condoms, it's what fertilizes your eggs. I don't know if you really need this much info, you probably know what sperm is, but I just want to be safe.
it's the slang for sperm :P