K9 an abreviated form for canine. The concept is to participate in a sexual form with a dog. Broader concept is bestiality. Think in terms of King Kong as a potential partner. It might work. The penis of a gorilla is much smaller than the penis of a human.

This could lead to lots of definitions for words that are bantered without thought to definitions. I can think of dork and squaw as two fascinating words when used correctly.