walled plain

American  

noun

1. a circular or almost circular area on the moon, sometimes with a floor that is depressed, usually partially enclosed by walls that rise to varying heights and that are usually lower than those of a crater.

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walled plain British  

noun

1. any of the largest of the lunar craters, having diameters between 50 and 300 kilometres

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Example Sentences

Usually the floor of a walled plain becomes brighter as the sun rises higher and higher in the sky, but Plato actually becomes darker under a high sun.

From To Mars via The Moon An Astronomical Story by Wicks, Mark

In the neighborhood of the south pole lies the large walled plain of Newton, whose interior is the deepest known depression on the moon.

From Pleasures of the telescope An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers by Serviss, Garrett Putman

The above comprise all the mountain ranges in the northern hemisphere of any prominence, or which have received distinctive names, except the Hercynian Mountains, on the north-east limb, east of the walled plain Otto Struve.

From The Moon A Full Description and Map of its Principal Physical Features by Elger, Thomas Gwyn

PONTECOULANT.—A great irregular walled plain, about 100 miles in length, near the S.W. limb, with a border rising in places to a height of 6000 feet above the floor.

From The Moon A Full Description and Map of its Principal Physical Features by Elger, Thomas Gwyn

I now directed M'Allister to steer across the lunar equator into the southern hemisphere, and our attention was soon attracted by a very large walled plain on the eastward side of our course.

From To Mars via The Moon An Astronomical Story by Wicks, Mark