When a guy hasn't had sex in a while, and all the sperm that he hasn't cummed, "backs up" into his brain. So now all he thinks about is having sex.
A play on the condition, kernicterus, in which unconjugated bilirubin deposits into the brain of a newborn, causing severe physical and mental problems.
Man, John has a case of spermicterus. All he does is talk about sex. He really needs to get laid.
A sex act in which, the male(s), while fucking twin females, cum into the mouth of one twin and she then spits that load into the mouth of the other twin.
A play on the actual condition in which during a twin pregnancy, arterial blood from donor twin passes through the placenta into vein of recipient twin. Essentially the donor twin gets less blood and the recipient twin gets more.
Man I had a great time with those twins yesterday. They even performed a twin-twin transfusion.