Basic Guidelines For English Spellings
A fissure or narrow channel on the moon's surface.‘He prefers looking in and near smallish craters and the rilles - long, sharp lines or faults.’
- ‘But we know that the Moon is not spherical: rather, it is mountainous in some regions, deep canyons and rills permeating the surface elsewhere, and it is pockmarked with craters, too.’
Mid 19th century from German (see rill).
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