Top Definition
When you discover that one of your parents has had sex with the parents of someone you know, that person is now your semen sibling.
I kept wondering why dad keeps on giving rachel wierd looks, turns out he fucked her mother and we're semen siblings.
by Shalmanese October 21, 2006
5 Words related to semen sibling

Free Daily Email

Type your email address below to get our free Urban Word of the Day every morning!

Emails are sent from We'll never spam you.