The action of performing anal sex in order to preserve ones vaginal purity. Most extreme religious couples practice this before marriage, although in almost all religious publications this is looked up as a worse offense.
In the case of homosexual relations, this is the only way for a men to perform intercourse with each other.
"Have you heard that Tom and Bill have a dry-erase board in their bed room?"
"No, whats it for?"
"I have heard that is used to keep score of who has had the most orgasms while they are saddlebacking each other. I also heard that they participate in the convergence practice after they finish."
When two anal gas excretions are mixed together to make one smell so horrible that it causes someone to pass out.
After Tom and Bill get done saddlebacking each other for hours on end, they like to end their romantic session by creating a big convergence for themselves from their newly stretched anal parts. Then they hold and caress each other softly while they slowly drift off to sleep.