1. A region of complete shadow resulting from the total obstruction or blocking of light.
2. The darkest portion of the shadow cast by an astronomical object during an eclipse, especially that which is cast on earth during a solar eclipse.
3. Te main dark inner cone of shadow cast by one body onto another body during an eclipse.

Any point lying within the umbra will observe a total eclipse of the object. The umbra is also the name given to the darkest part of a sunspot.