Airtight (adjective)

1. Sealing an area or container so that no air can pass through.
2. Making something so that it cannot be criticized or proven false.

Origin:

From air + tight, from the sense of preventing air from escaping or entering.

Examples:

1. The container was airtight to preserve the food.
2. The seal on the lid of the jar was airtight to keep the contents fresh.
3. The argument was airtight and left no room for counter argument.
4. The evidence was airtight and left no doubt of his guilt.
5. The chamber was airtight to maintain the required pressure.