1) Of, or pertaining to, rhinoceroses.
2) The use of the nose or nostrils for erotic purposes. From 'rhinal', meaning 'of the nose', and 'erotic', the meaning of which is obvious.
Ted: So how was the zoo?
Mark: Ah, we had a lot of fun. We even participated in rhinocerotic activity behind some bushes.
Ted: Oh, that does sound fun...