1. Sucker for sb./sth.,
Just call me a sucker for a man in uniform.

I’m always a sucker for chocolate. I’m on a diet, but I love to try a piece.

David is a sucker for this kind of music. If you get him the CD, he’ll be crazy.

2. To root for someone,支持某人

Good luck with your interview. I’ll be rooting for you.

I’m rooting for Guoan,Beijing. Are you rooting for Shide, DaLian

3.  Rat someone out, 出卖谁

There’a a spy in our company, we need to rat hime out.

I know Lily Cheated on the test. Should we rat her out?