Tetris sex

I don’t quite understand it but “Tetris sex” is a very popular search term when I look through my stats, with quite a few people making it here after having looked for it.

Someone has suggested that these may just be idiots looking for “Tantric sex”, but I attract a special kind of pervert, so they may very well mean tetris sex.

The problem is discovering what tetris sex actually entails, suggestions, demonstrations and video/picture submissions are welcome.