rille also rill (ril)
1. A long, narrow, roughly straight channel or groove on the surface of a solar system body like a planet or moon.
2. Variant ofrill.
[GermanRille; see rei- in the Appendix of Indo-European roots, fromLow Germanrille; see rei- in the Appendix of Indo-European roots.]
(click for a larger image)rille
Ariadaeus, a lunar rille, photographed in 1969 by the crew of Apollo 10
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