exclam. Did you hear me?; Are you aware that I am talking to you? A: I don’t want any of that. B: Here, have some. A: Hello? No, I don’t want any.
Did you hear me? Do you really mean that? This slangy term is not the conventional greeting, but pronounced with strong stress on the second syllable (hel-LO?), it acquired this new meaning in the late 1900s. For example, “You mean you’ve never heard of America Online? Hello?” It is on its way to clichédom.