1. slang To physically attack one, as with punches and other blows, such that they suffer significant injury. This phrase can be used both literally and hyperbolically. Primarily heard in US. Our neighbor is in the hospital because a burglar beat the tar out of him. I'm worried that the captain of the football team will beat the tar out of me if he finds out that I'm secretly seeing his girlfriend. If you ever scare me like that again, I'll beat the tar out of you, I swear!

2. slang To defeat one decisively in a competition. Primarily heard in US. The final score was 17-1? Wow, we really beat the tar out of that team!