‘I wish to propose to you a new term, one that has been missing for a long time: “circlusion.” It denotes the antonym of penetration. It refers to the same physical process, but from the opposite perspective. Penetration means pushing something – a shaft or a nipple – into something else – a ring or a tube. Circlusion means pushing something – a ring or a tube – onto something else – a nipple or a shaft. The ring and the tube are rendered active. That’s all there is to it.’
– Bini Adamczak, On “circlusion”