When a person kisses, licks, or sucks another person's GENITALS to make them feel good. Putting a penis into a mouth is one way. Another way is to touch the penis, anus, clitoris or vulva with the mouth, lips or tongue. People can get STDs this way. It doesn't matter if they are doing it to someone or if someone is doing it to them. Either person could get INFECTED. This could happen if BLOOD or sexual fluid got inside someone's mouth, or there is contact with a sore from a disease such as HERPES or SYPHILIS. Also, if INFECTED blood from someone's mouth got inside another person's penis, anus, clitoris or vulva this could happen. Moisture barriers and non-lubricated latex condoms can be effective in stopping someone from getting infected. ORAL SEX is said to be less risky than ANAL or VAGINAL INTERCOURSE. Slang terms: Sixty-nine (69), when two people have oral sex with each other at the same time. See also, cunnilingus and fellatio.