Military term for an operation in which multiple things have gone wrong. Related to “SNAFU” (Situation Normal, All Fucked Up”) and “FUBAR” (Fucked Up Beyond All Repair).
In radio communication or polite conversation (i.e. with a very senior officer with whom you have no prior experience) the term “clusterfuck” will often be replaced by the NATO phonetic acronym “Charlie Foxtrot.”
And 53 more definitions on UrbanDictionary.com. Wiktionary.org reports the etymology of the term.