atmospheric air specially cleaned so that it contains less than 0.1 ppm of hydrocarbon impurities; it then is usable in laboratory procedures such as versions of gas chromatography in which sufficiently pure air may serve as a carrier gas.

(usually used attributively, finance) A non-existent coupon. / (finance) A financial security that does not pay interest periodically.

(computing, idiomatic) (of vulnerability) newly discovered, and therefore still not fixed and possibly exploited by hackers or other criminals

(computing, idiomatic) vulnerability that has been discovered recently, and is yet unpatched or unmitigated; zero-day vulnerability

(mathematics, of a function) Being equal to the zero function and not merely zero at a particular point in its domain.

Resulting in neither a surplus or deficit because gains and losses cancel out.

plural of zero point

(of cattle) Kept in enclosures and never let out to graze.

(epidemiology) The initial patient in the population of an epidemiological investigation.

The site of the former World Trade Center towers in New York City destroyed on 11 September 2001.