also water-tight
1.
Something that is ~ does not allow water to pass through it, for example because it is tightly sealed.
The flask is completely ~, even when laid on its side...
ADJ
2.
A ~ case, argument, or agreement is one that has been so carefully put together that nobody will be able to find a fault in it.
The police had a ~ case. They even got his fingerprints from that glass cabinet.
ADJ