A sexual position involving a man in a reclining position who is being ridden by a gastropod, such as a snail, that is facing his feet with the side of its body that contains the cerebral ganglia. The man may either enter via the snail's genital pore (though not necessary due to the snail's asexuality) or he may copulate through the pneumostoma.
Dave ensured that he didn't rupture his snail's dart sack with his kinky gyration by instituting a safeword during a rousing session of reverse cow-snail.
Jason's favorite way to fuck a slug is reverse cow-snail so he doesn't have to look at the damn things creepy eyeballs at the end of its tentacles.
The best thing about reverse cow-snail is that at least you're fucking a bug.