1) An empahtic response to someone's abject whining (and crying), usually about tasks that someone is required to do, with the implication that the whiner is an punky, slacker, immature, lazy-assed, cry-baby. The words are radio phonetics for the letters W-F-W, and in this case the letters stand for, "Whaaa Fuckin' Whaaa," hence an emphatic declaration of an abject lack of characer. This also shows that its origin is in the military. A less emphatic expression is simply "Whaaa!"
2) Can also be the response to abject whining (and crying) regarding how hard someone's life is, when in reality they are quite coddled and and their lives are almost excessively comfortable, and the expression indicates how the whiner is an ingratious, cowardly, punky, slacker, immature, lazy-assed, cry-baby.
Ingratious, Cowardly, Punky, Slacker, Immature, Lazy-assed, Cry-baby: Aww, how come you won't get me a Lamborghini Diablo?
Person in authority: Whiskey Foxtrot Whiskey, dildo!