Word Study
rille
CIDE DICTIONARY
rille, n. [G. rille a furrow.].
One of certain narrow, crooked valleys seen, by aid of the telescope, on the surface of the moon. [1913 Webster]
OXFORD DICTIONARY
rille, n. (also rill) Astron. a cleft or narrow valley on the moon's surface.
Etymology
G (as RILL)
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