(military) An area, often on a border between military factions, in which military forces and operations are prohibited.

An area of a street or a parking lot designated for the loading or unloading of passengers, baggage or freight, or short-term parking for that purpose.

(US, California) An area of a street where the curb has been painted white, indicating that the spot is only to be used for the immediate loading or unloading of passengers, baggage or freight, or for short-term parking, and (in some places, such as airports) that a vehicle is not to be left unattended.

(physics) The stage in the flow or a fluid during which it changes from laminar to turbulent / (geology) The region between the upper and lower mantle characterized by a rapid increase in density

The area in which the baton must be passed from one runner to another during a relay race.

(mycology) A ring of fibers on the stem of a mushroom that is not well enough defined to be called an annulus.

(climbing) Land at sufficiently high altitudes that there is not enough oxygen to sustain human life.

Alternative spelling of dropzone / relegation zone

The photic zone

plural of zone defense