(historical) A former area between Saudi Arabia and Iraq, abolished 1991.

(botany) The area in a plant's leaf, stem, or fruit stalk, where the abscission layer if formed along with weakened sclerenchyma, absent collenchyma, and dense cytoplasm.

An area with no life. / (ecology) An area of the ocean where oxygen levels are too low to support life, especially as a result of pollution.

(of a tidal coast) The intertidal zone / (of a non-flowing, non-tidal body of water) The zone of shallow water to the limit at which plants root.

(geography) The oceanic realm consisting of the deep ocean, typified by a dearth of plant life, and plentiful carnivorous animals that are able to withstand extreme pressure.

(geology, often humorous, by analogy to erogenous zone) A region characterized by mountain-building.

(UK) A street or group of streets designed primarily to meet the needs of pedestrians, cyclists, children and residents, and where motor traffic is limited.

A theoretical orbital zone around a star that will result in an Earth-like planet existing in an orbit in the zone having a runaway greenhouse effect, similar to that found on Venus in our Solar System. The inner edge of the zone is where solar radiation is intense enough to strip the atmosphere of a planet away. The outer edge is where solar radiation is insufficient to power a runaway greenhouse.

A feature of some volcanoes, especially the shield volcanoes of Hawaii, in which a linear series of fissures in the volcanic edifice allows lava to erupt from the volcano's flank instead of from its summit.

A diet that advocates consuming calories from carbohydrates and protein in a balanced ratio.