A military term for being in a bad situation, a total mess, or when all kinds of things have gone wrong­­—but with the caveat that it could have been prevented with correct planning and less arrogance or stupidity on the part of the main decision makers. The “cluster” most likely refers to the cluster of oak leaves that is part of a military officer’s insignia. This helps explain why a “cluster fuck” is due to bad decisions by the officers that the rank and file are left having to deal with