A big flop; a complete failure (often used colloquially for box-office bombs or major flops).
あの映画は期待されていたが、公開初日で大コケした。
That movie was highly anticipated, but it was a big flop on its opening day.
新商品のキャンペーンは準備不足で大コケに終わった。
The new product campaign ended up a complete failure due to poor preparation.
舞台で主役が転んで観客がどっと笑い、大コケになった。
The lead actor fell on stage and the audience burst out laughing — it turned into a big flop.