— umbral , adj.
/um"breuh/ , n. , pl. umbras, umbrae /-bree/ .
1. shade; shadow.
2. the invariable or characteristic accompaniment or companion of a person or thing.
3. Astron.
a. the complete or perfect shadow of an opaque body, as a planet, where the direct light from the source of illumination is completely cut off. Cf. penumbra (def. 1a).
b. the dark central portion of a sunspot. Cf. penumbra (def. 1b).
4. a phantom or shadowy apparition, as of someone or something not physically present; ghost; spectral image.
[ 1590-1600; ]