Incesturbate 

To masturbate your identical twin.

"What did you guys do last night?"
"My twin brother and I attempted to incesturbate for the first time"

Incesturbate by Garooshnar December 20, 2016

Investurbate 

When you can't determine whether something is hot or not, so you decide to put it to the masturbatory test.

I'm 50% certain this HomeGoods ad is heating me up, but I'm not sure. Time to investurbate.

Yahoo Answers couldn't tell me whether or not I'm sexually attracted to Ansel Adams' photographs, so I had to do some ground-level investurbation. I'm not. We're good.

Investurbate by asthmaticdan October 20, 2015

incesterbation 

When you have sex with your clone, your doppelganger, or a version of you from a parallel universe.

If you clone yourself and then have sex with the clone, it is neither incest nor masturbation, but both: incesterbation.

incesterbation by Anon Imus November 16, 2006

Incesturbation 

To have sex with your clone.

I engaged in some hot incesturbation last night!

Incesturbation by livejamie June 7, 2004

incepturbation

jerking off on a video of you jerking off while recording yourself jerking off to a video of you jerking off.

dave: i walked in on greg's incepturbation session last night. he had the whole setup, it was gross!

incepturbation by peetr March 31, 2013

Incesterbation 

The act of having sex with your clone; a mix of masturbation and incest.

Spotti cloned herself and I caught her incesterbating, and it was awesome. It was some pretty hot incesterbation.

Incesterbation by Taliaa July 16, 2007

Incesturbation 

When you clone yourself and then have sex with the clone.

The University loaned me their cloning device; I've always wanted to try incesturbation.

Incesturbation by lclaymaz May 15, 2015