This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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adj. Impermeable by air.

adj. Having no weak points; sound: an airtight excuse.

adj. Being impermeable to air or other gases.

adj. Having no weak points or flaws (as in an "airtight" argument).

"(Store leftovers in airtight container at room temperature, for up to 3 days, or, ahem, in the freezer until your resistance gets the better of you.) [printable recipe coming soon]"

tight    invulnerable   

air-tight stove   

uncontradictable    undeniable   

water-tight    wood-burning    coal oil    vacuum-sealed    propane