1. an alien who does not have the necessary documents to be on earth.
2. illegal ownership of alien.
1. "Why's the alien so sad?"
"He's about to be launched into space because he is an illegal alien. That's why he is sad, and he will die."

2. "I have an alien at home."
"If you have an alien at home, he would be an illegal alien. You are not allowed to own aliens here."
by Steamy Bunny August 28, 2022