"Singled out" means that a person is treating another person differently from others; also that they are calling attention to the person for some reason, generally in front of other people.. It usually isn't nice but can be if they are being noticed (singled out) for something good.... :) Examples: "He singled her out as being the only short person in the room." (not nice) "He singled her out as being the only college graduate in the room. (nice to the person being singled out but possibly insulting to others)

“To single out” means to select or draw attention to a group of people or objects that is smaller than the original group. “Out of all of my classmates, my professor singled me out by asking me to summarize the book after the test.” “The bar owner singled out all of the English speakers in his bar by asking them to sing a popular English song.”