vacuum; a space entirely devoid of matter or containing extremely low pressure gas

(figurative) an environment isolated from society or other people

(figurative) a state of suspension or a gap where nothing is happening and no one has control

(slang) not wearing any underwear

(Buddhist) the ultimate reality where all things are seen as having no inherent, independent existence

short for 真空管 zhēn​kōng​guǎn; a device that controls electric current flow in a high vacuum between electrodes