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Ariadaeus, a lunar rille, photographed in 1969 by the crew of Apollo 10
rillealso rill (rĭl)
1. A long, narrow, roughly straight channel or groove on the surface of a solar system body like a planet or moon.
2. Variant of rill.
[German Rille; see rei- in Indo-European roots, from Low German rille; see rei- in Indo-European roots.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
(Astronomy) a variant of rill3
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014