1. A man/woman (whatever you're into) who beats their wife.
2. A kind of shirt worn by above said people.
1. Jorge: Hey, Bill! How was your wife last night?
Bill: Yeah, she didn't want my big, hard cock last night. So I became a wife beater.
2. Can I borrow your wife beater, bro?
Nah, sorry, it's my life blood man. I gotta wear it for a certain occasion tonight.