(physics, chemistry) A technique used to purify a metal, semiconductor or other solid in which a heating system slowly causes a series of molten zones to traverse the solid, leaving purer material behind it.

The region, between the Tropic of Cancer and the Tropic of Capricorn, characterised by a hot and humid climate; the tropics.

Any large portion of the Earth's land area which has a generally uniform climate and soil and therefore a high degree of uniformity in the composition of species; a number of different classifications have been proposed by different people.

The part of the near-surface body of an ocean or lake that receives enough sunlight for photosynthesis to be possible.

(oceanography) That part of the deep body of an ocean or lake that receives insufficient sunlight for photosynthesis to be possible.

The forehead and nose considered together as a region of the face that can, in some people, produce excess sebum compared to other parts of the face.

(military) An area into which a designated ground unit or fire support ship delivers, or is prepared to deliver, fire support. Fire may or may not be observed.

(military) A tactical subdivision of a larger area, the responsibility for which is assigned to a tactical unit; generally applied to offensive action.

(military) Rear part of a theater of war or theater of operations (behind but contiguous to the combat zone) which contains the lines of communications, establishments for supply and evacuation, and other agencies required for the immediate support and maintenance of the field forces. Also called COMMZ.

An area into which entry by a single individual is prohibited; commonly an area with accessibility to a nuclear weapon.