noun

• 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.’

  More example sentences

  • ‘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.’