airtight

Impermeable to air or other gases.

Tupperware founder Earl Tupper in 1946 introduced its plastic products to the public, and subsequently patented their flexible airtight seal.

Having no weak points or flaws.

We have an airtight argument they won’t be able to punch holes in.

airtight alibi

Highly reserved in some matter, particularly tight-lipped or tight-fisted.

when Roger asked for $100 to take the preliminary steps to establish his claim, Mike yelled like a Hebrew auctioneer, for he was air-tight and squeezed a dollar until the woman on it yelled.

He was ‘air-tight,’ close-mouthed, and had but few confidants or intimate friends, but numerous acquaintances.

Triply penetrated simultaneously in the vagina, anus and mouth.