When a person on Facebook decides they don't want to continue the conversation on a post anymore. So they "Like" the last comment, like a complete asshole. It's a combination of "liked" and "comment". A basic way of saying "Fuck you, I don't feel like responding", but in a much nicer, and more subtle way.
Guy #1: "Did she ever respond to that post?"
Guy #2: "Nope, she left me hanging. I got Cliked.