- of or like a shadow or shadowy apparition:Smoke was rising and beginning to coat the clouds a deep, umbral black.In an instant the vampire’s corporeal form dematerialized into an umbral form that quickly merged with the surrounding cover of night.
- Astronomy.
- relating to or being the complete shadow of an opaque body, such as a planet, where all direct light from the source of illumination is cut off:It was to be a very deep eclipse, with the moon passing very close to the center of Earth's umbral shadow.
- relating to or being the dark central portion of a sunspot:Umbral flashes—powerful brightenings that shock the darkest part of the sunspot—appear continuously every 2 to 3 minutes.
