twincest 

Slash (mainly) between twins.

1. Elladan and Elrohir, twin sons of Elrond of Imladris. From lotr
2. Weasley twins from HP

twincest by brat July 3, 2004

Twincest 

Strong emotional and physical attraction between twins.

Did you see Tammy and Sammy together last night? Total twincest!

Twincest by powergannon July 23, 2010

twincest 

The act of twins engaging in incest.

Twins having intercourse.

"I heard John and Eli got busy last night."
"Dude, they're twins!"
"Yeah, twincest."

twincest by areyoureallyreadingthis? April 19, 2010

twincest 

3rd person masturbation

Twins might justify twincest with each other by thinking of it as 'nothing different than masturbating from the 3rd person point of view'

Twincest between guys may often be referred to as a '3rd Person Shooter'

Mutual '3rd Person' Masturbation

twincest by Jack U. Hoff April 28, 2008

twincest 

The fascination, lustful feelings or fetish with twins. Typically those featured in any adult themed entertainment.

"Did you see those hot twins online?"
Terry and Jerry are this week's featured twins in xxx.twincest.com.
The twincest I feel for those doublemint girls is beyond belief.

twincest by mitcherrbahn September 8, 2010

Twincest 

When twin brother and sister have sex with each other. Something fans of Rosiel/Alexiel pairings from Angel Sanctuary write about in fanfics.

We're twin brother and sister who engage in twincest together.

Twincest by Michael & Michele September 23, 2005

twincest 

When twins are in love with each other

Benji & Joel Madden (from good charlotte incase ya didnt know) - what a sight that would be...sadly the rumours arent true...are they...???!!?? ^_^ We'll just have to make do with the twincest fan fics!

twincest by emo*ass February 16, 2004