When you put your toes in between the toes of another person. Often done as an act of friendship or as a romantic gesture, interlocking dogs is a very powerful action that will strengthen the relationship (platonic or otherwise) between two people
When yourself and another person with an anus that is shaped like a cone from prolapse, press together anally and interlock with each other. Sometimes it gets even more tasty when one person needs to shit.
A situation for a couple(man/woman), in which the woman, procures a double sided dildo. Preferably one with a good amount of give. The process involves locking ones genitalia, and then the double sided dildo is placed within both buttholes.
When a male puts his foreskin over another mans helmet/bell end then the second man places his( the second foreskin) over the first gentlemans foreskin