To believe a person is better or more important than others or above reproach. (Note: If thought about oneself, it means that they are arrogant, conceited, or self-absorbed. If someone thinks this of another person, it means that they love or admire that person to such a degree as to be blind to any of their potential faults.) Tom has acted like he's such a hotshot after getting the promotion. He thinks the sun shines out his backside! He's absolutely head-over-heels in love with Mary. Even though I find her a bit irritating, he thinks the sun shines out her backside.