um·bra 
(ŭmbrə)
(ŭmbrə)n. pl. um·bras or um·brae (-brē)
1. A dark area, especially the blackest part of a shadow from which all light is cut off.
2. Astronomy
a. The completely dark central portion of the shadow cast by the earth, moon, or other body during an eclipse.
b. The darkest region of a sunspot.
[Latin, shadow.]
umbral adj.
umbra