the act of sticking eight fingers into an anal cavity facing your hands outward and sticking your penis in-between the backs of your hands and commencing coitis.
The artificial manufacturing of the universe's most precious creation, vagina -- if god made anything better than pussy, he has kept it for himself. The Frankengina is a similar perversion of god's intent as the one described in the sci-fi classic "Frankenstein."
A Frankengina is created by taking a real working dick and turning it into a non-working, fake pussy. Then the excess/left over penile and scrotal tissue is used to manufacture artificial beef curtains that still smell and taste like ballsack when you're munching them.
Just the nauseating/horrific thought of being tricked into going "downtown" on a Frankengina is enough to swear off being a "vagitarian forever."