When a women becomes incredibly turned on and is about to have sex with a guy, but the guy decides not to have sex with her or it just doesn't happen due to unforeseen circumstances.
AKA The female version of blue balls.
Girl 1: "He was so hot and right before we fuck he passes out, giving me a particularly severe case of blue cunt."
Girl 2: "That sucks."
Guy 1: "Did you fuck that girl last night?"
Guy 2: "Nah dude I realized I had to go somewhere important and left her house early, she must of had some bad blue cunt."