Definition of umbra
1a
: a conical shadow excluding all light from a given source
specifically
: the conical part of the shadow of a celestial body excluding all light from the primary source
b
: the central dark part of a sunspot
2
: a shaded area
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Merriam-Webster unabridged
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Time Traveler for umbra
The first known use of umbra was in 1638
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