Definition
1 a : 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

Did You Know?
The Latin word umbra (“shade, shadow”) has given English a range of words in addition to umbra itself. An umbrella can provide us with shade from the sun. So can an umbrageous tree. (In this case, umbrageous means “affording shade.”) The connection to shade or shadow in other umbra words is less obvious. When we say someone takes umbrage, we mean they take offense, but in times past people used the word as a synonym of shade or shadow. These two senses of umbrage influenced umbrageous, which can mean “inclined to take offense easily” as well as “affording shade.”

Examples
“Thus far, though, no one on the ISS has managed to ‘thread the needle,’ with a view passing through the narrow umbra of a total solar eclipse.” — David Dickinson, Sky & Telescope, 4 Aug. 2017