1. Of or pertaining two the the act of two identical female twins performing oral sex on one another.
2. A special type of masturbation that can only occur between two female identical twins.
See also twinnillatio.
Not only was I doing two chicks at the same time, they hopped off of me and started eating each other out in a mad session of twinnilingus.
"Those Coors Light girls are definately down with twinnilingus."