Slang: "let on"
    “But at the same time, realizing I was in a room filled with killers, how much do you let on that you’re petrified?”
    Leonardo DiCaprio talking about working on his latest movie, The Departed.
    Definition: reveal; show; express
    Use
    Leonardo DiCaprio is wondering how much he should reveal about his true feelings. Should he let on that he’s scared? Should he “show” that he is scared?
    If you like a girl, you might not want to let on that you like her. You might not want to show her your feelings.
    Say you tell a guy that you don’t want to date him. He says it’s no big deal. You could tell your friends, “I told Jerry I just wanted to be friends. If was upset, he didn’t let on.” Meaning, Jerry didn’t reveal whether he was upset.
    Examples
    “If I let on that I’m in love with him, it will scare him off. I have to be cool.”
    “If you see a bear in the woods, don’t let on that you’re scared. They can smell fear!”
    “I felt like crying when Ian broke up with me, but I didn’t let on. I pretended like I was fine.”