When twins get together in a odd and disturbingly immoral relationship to the out side world. A mix of incest and twins.
Laurie: damn you see those blonde twins over there, they are having a twincestual relationship
Josh: that is gross, and not to mention immorally disturbing.
Laurie: damn straight it is,andi thought the girl was hot.
Josh: obviously so did her brother.
Laurie: just like those gay scots the proclaimers.
Josh: lool
by Chizeej- on behalf of Lozz April 17, 2007
When two twins both female do anything sexual to either each other or to someone else with each other.
The twins both screamed at the word twincest.
by PainCorp July 11, 2004
Something that is so wrong in real life but so right in anime.
Giving a whole new meaning to "go fuck yourself".
If you ask me, the sexiest twincest is Hitachiincest (Hikaru x Kaoru Hitachiin) from Ouran Highschool Host Club. But my friend hates it. But then again she hates yaoi sooooooooo...
by 730cute September 17, 2014

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