A child concieved in a lavender marriage. In which, at least one of the spouses was homosexual. This is usually to make others think that the spouse(s) are completly heterosexual.
Tommy- "My parents are gay"
Mike- "But don't you have a mom and a dad"
Tommy- "Yeah, but my parents married each other and had me to try and convince themselves and others that they were straight, but they aren't."
Mike- "Ohhh, so you're a lavender baby."