Practice of filling all 3 orifices of a female by either penis, or objects.
A penis in the ass, pussy and mouth at the same time, or a combination of penis and vibrator/dildo.
My wife likes to be made airtight by having my cock in her mouth, a plug in her ass, and a vibrator in her pussy.
Becoming airtight, or airtighting, is when a woman has sex with three men at the same time, and receives the pleasure of having her vagina, anus, and mouth penetrated at the same time, giving the impression that all of her orifices are sealed, not allowing air to either enter or escape, hence airtighting.
I love being shared by three men at the same time, and them Airtighting me.