noun
A region of space that contains no matter.
The Wards are open-topped, with skyscrapers rising from the superstructure. Towers are sealed against vacuum, as the breathable atmosphere envelope is only maintained to a height of about seven meters. The atmosphere is contained by the centrifugal force of rotation and a "membrane" of dense, colorless sulphur hexafluoride gas, held in place by carefully managed mass effect fields.
The condition of rarefaction, or reduction of pressure below that of the atmosphere, in a vessel, such as the condenser of a steam engine, which is nearly exhausted of air or steam, etc.
a vacuum of 26 inches of mercury, or 13 pounds per square inch
Ellipsis of vacuum cleaner.
A spacetime having tensors of zero magnitude.
A ground state of a quantum field or of local spacetime, or more abstractly the lowest-energy state of a system.
verb
To clean (something) with a vacuum cleaner.
“Who in the world cleans an attic? That's like vacuuming a shed.”
To use a vacuum cleaner.
To optimise a database or database table by physically removing deleted tuples.
But the advantage of an auto-vacuumed database is that when B-tree pages are no longer needed, they are moved to the end of the database file and then the database file is truncated, thus returning the unused pages back to the filesystem.