1. 不透气的；气密的；密封的
If a container is airtight, its lid fits so tightly that no air can get in or out.

2. （不在场证据或案件、契约、论据）无懈可击的，没有漏洞的，严密的
An airtight alibi, case, argument, or agreement is one that has been so carefully put together that nobody will be able to find a fault in it.

1. not allowing air or gas to pass in or out

Synonym: air-tightgas-tight

2. having no weak points

e.g. an airtight defense
an airtight argument

Synonym: air-tight