debacle
An event or enterprise that ends suddenly and disastrously, often with humiliating consequences.
figuratively
The event proved to be a great debacle for the partisans of this prognosticator.
A breaking up of a natural dam, usually made of ice, by a river and the ensuing rush of water.
[…] so that in extreme cases the latter may even be dammed up for a time, and a debacle be the consequence, when the main river overcomes the resistance opposed to it, […]
Where it comes from
From French débâcle, from débâcler (“to unbar; unleash”) from prefix dé- (“un-”) + bâcler (“to dash, bind, bar, block”) [perhaps from unattested Middle French and Old French *bâcler, *bacler (“to hold in place, prop a door or window open”)], from Vulgar Latin *bacculare, from Latin baculum (“rod, staff used for support”), from Proto-Indo-European *bak-. Also attested in Old French desbacler (“to clear a harbour by getting ships unloaded to make room for incoming ships with lading”) and in Occitan baclar (“to close”). The hypothesised derivation from Middle Dutch *bakkelen (“to freeze artificially, lock in place”), a frequentative of bakken (“to stick, stick hard, glue together”) no longer seems likely due to the lack of attestation of *bakkelen in Middle Dutch and by it having the limited meaning of "freeze superficially" in Dutch.
Adapted from the Wiktionary entry debacle (CC BY-SA 4.0).