What's "dull" mean? In what context can I use this?

Native speaker’s answer
Rebecca
"Dull" is another way of saying "boring" or "uninteresting." The speaker isn't trying to say that he became duller as a person, but rather, that he tried to dull his emotions or become more distant with his fans as a result of the emotional hurt he received before. Ex: They say that John is a dull person, but I find him quite interesting and fun. Ex: After being rebuffed by her friends several times, her personality turned dull and closed-off.