Anal intercourse. Legally, the term may include other types of perversion such as bestiality.
A paraphilia variously defined by law to include sexual intercourse with animals, and mouth/genital or anal contact between humans.
Anal sexual intercourse between men.
In medical usage, anal intercourse; which is usually homosexual, but may involve an animal or be heterosexual.
Sexual intercourse using the anus. This may be homosexual, heterosexual, or between man and beast.
Anal intercourse. Sodomy may occur between men, between a man and a woman, or between a man and an animal (bestiality).
Sexual contact between humans and animals, or anal contact between humans.