when you have done something inexorably foolhardy, and then you, have been stuck with the mope. nothing that you can say or do will regain you a measure of dignity that day. you are stuck with the mope, causing you a bastion of shame until you can incrementally redeem yourself.
gentleman #1: *says something inexcusably dull or vulgar*
gentleman #2: "..."
gentleman #3: "holy shit gentleman #1, you are fucken, stuck with the mope."
gentleman #2: "agreed, you got the mopemouth somethin' awful motherfucker."
gentleman #1: *shamefully recedes into background plotting redemptive act*
To put someone, or something, to complete shame, or humiliation, and to better it in every capacity; to utterly outdo, outperform or outwit. The phrase is used to conjure sentiments of shaming to the point of using that thing for the lowly task of mopping the floor with. Generally used in past, or more rarely, future or prospective tense.