長ちょう蛇だを逸いっす

expression, godan verb (-su)

miss a big chance; let a golden opportunity slip by

Idiomatic expression meaning to fail to seize a major opportunity. The image is of letting a long snake escape. Can also refer to allowing an enemy to get away. Often used with する as 長蛇を逸する.

• 彼かれは優ゆう勝しょうのチャンスを長ちょう蛇だを逸いっした。

  He missed a golden opportunity to win the championship.

• 敵てき将しょうを取とり逃にがし、まさに長ちょう蛇だを逸いっす結けっ果かとなった。

  They let the enemy commander slip away, truly a case of letting the big one get away.