Definition of rille in English:

rille

noun

(also rill)
Astronomy
  • 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.’

Pronunciation

rille

/ril/ /rɪl/ /ˈrilə/ /ˈrɪlə/

Origin

Mid 19th century from German (see rill).