The "backwards" partner in the gay relationship, or to further explain for those slow in the head, the guy who takes it in the ass. Verb form signifies getting rearended.
The alias Ranma Saotome (from Ranma 1/2) uses when he is female and around his mother. He stops using this around Volume 33, when his secret is revealed. Anyone who hasn't read or seen Ranma 1/2 SHOULD!!!!