ˈgu̇(ə)r noun
( -s )
Etymology: German guhr, gur; akin to Middle High German gern to ferment, Old High German jesan — more at yeast
1. : a loose earthy deposit from water occurring in the cavities of rocks, being mostly white but sometimes red or yellow, and consisting of a varying mixture of clay or ocher
2.
[by shortening]
: kieselguhr