watertight

1. ADJ Something that is watertight does not allow water to pass through it, for example, because it is tightly sealed. 不透水的

The flask is completely watertight, even when laid on its side. 這水瓶即使平放也不漏一滴水。

2. ADJ A watertight case, argument, or agreement is one that has been so carefully put together that nobody will be able to find a fault in it. (事實、論點、協議等) 嚴密的; 無懈可擊的[英國英語]

If she could just establish the time the picture had been taken, Mick would have a watertight alibi. 衹要她能確定拍這張照片的時間，米尅就可以有一個無懈可擊的不在現場的証據。