[Weeble]

Good detail in that link serg3d!

I only used the term 'vacuum' to describe a pressure state temporarily below ambient as I feel that the phrase 'negative overpressure' (which is the technically correct one) is clumsy and can be misleading.

The sense I meant was thus "A space in which the pressure is significantly lower than atmospheric pressure."

I can't imagine my bank manager complaining about "negative overfunding" in my account.