Slur for a promiscuous, fertile pussy-haver who tells you to pull out and ejaculate on her back during doggy, making her back wet with your seed.
That wetback whore I cheated on you with was a good fuck!
A racial slur mainly targeted at Mexican laborers, illegal immigrants, and Mexicans and Hispanics in general.
"Look at those wetbacks" said the man pointing at a group of Mexicans doing yard work.