A derogatory term referring to illegal alien from Latin America who, because s/he cannot swim, enters the U.S. by crawling under the fence, causing his/her back to get severely scratched.
Person 1 white trash: "Hey, Juan. Like, your Mom's a total wetback. They should deport y'all back to Mexico."
Person 2 (Hispanic respondent): "Actually, Billy Bob, you ignorant white trash racist pendejo, my Mom came from Guatemala and crawled under the fence carrying me. So, we're both scratch backs."
Overprotective Father: Let me remind you that it's MY daughter you're dating. You'd better have her back home by 11:00, or so help me, you WILL marry her!