rill
1. rill \'ril\ n [D ril or LG rille; akin to OE ri-th rivulet] : a very small brook 2. rill vi : to flow like a rill 3. rill or rille \'ril\ \'ril, 'ril-*\ n [G rille, lit., channel made by a small stream, fr. LG, rill] : any of several long narrow valleys on the moon's surface