Tert is an action of randomized, public sexual affection. When tert is only said once by a person, it is rape. But if the victim or other person replies "Tert" Back, it agrees to mutual sexual relations. But if the victim just says yes, He/She is accepting the public rape.
On the science fiction tv series "Alien Nation", "tert" is the derogative slang term that the Newcomer aliens (The Tenctonese) use for humans. Just as the humans call Newcomers "Slags", disaffected Tenctonese youth can be heard referring to humans as "Terts".