Definition of rille in English:

rille

(also rill)

noun

Astronomy
  • A fissure or narrow channel on the moon's surface.

    rill
    • ‘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.’
    • ‘He prefers looking in and near smallish craters and the rilles - long, sharp lines or faults.’

Origin

Mid 19th century: from German (see rill).

Pronunciation:

rille

/rɪl/