Noble idiot 

A person who 'sacrifices' their own happiness with the assumption that they are bringing happiness to the person they are sacrificing for, when in fact, this sacrifice makes the other person even more unhappy.

Prime Minister: I'm in a contract marriage with you and now you're telling me that my real missing and presumed dead wife is really alive?
I: Yes. So I'm going to leave you even though we've decided we actually love each other and want to marry for real now.
Prime Minister: But I don't want my old wife back. She pretended to be dead so I hate her now. But I love you, you noble idiot.
I: Tough. I'm gonna travel the world and write a kids book. Get back with your old wife.
*Prime Minister proceeds to not get back with old wife because he hates her while I mopes because she's depressed she left the Prime Minister*

Noble idiot by kshyt0385 February 5, 2014

Noble Idiot 

The one who even after someone cheats on them several times makes fun of them behind their back, and gets their heart broken too many times to count. Will still be at the door with flowers.

Guy1: I banged Tammy
Guy2: Dude, she has a boyfriend
Guy:1 Really? I'm not the only one who banged her, she was pretty hammered. What a noble idiot.

Noble Idiot by Interdan March 5, 2009