Synonymous with sodomy and referring to "unnatural" sex acts, including copulation, either between two persons of the same sex or between a person and an animal (the latter act also known as "bestiality").
Most countries outlaw bestiality but homosexual activity is gradually being decriminalized.
Judicially, circa 1858, the Supreme Court of Indiana (had to consider a complaint framed as follows about a certain "Mary" who allegedly "did have pups in Ohio, and it can be proved. She had two pups by a haystack; thereby meaning that she had been guilty of bestiality, or the crime against nature."
The Court:
"Bestiality is a connection between a human being and a brute of the opposite sex. Sodomy is a connection between two (male) human beings ... named from the prevalence of the sin in Sodom."
In Canada, buggery was struck as an offence in 1988 and in its place, anal intercourse is now prohibited except as between consenting adults (¶159).