1 [+bottle, container, seal] hermético The flask is completely watertight, even when laid on its side The watertight seal will keep contents perfectly dry
[+compartment, boat, ship] estanco The batteries are safely enclosed in a watertight compartment
[+door] de cierre hermético The watertight doors were closed
2 [+alibi] perfecto He was sentenced to 15 months despite having a watertight alibi
[+agreement] sin lagunas Neil has a contract with us and it's a watertight agreement
[+guarantee, embargo] sólido; [+argument, theory] irrefutable To make the embargo watertight, it would be necessary to organise a military blockade The UN want to secure a watertight guarantee that the army won't invade again The theory is far from watertight, but it is accepted by the authorities