the invariable or characteristic accompaniment or companion of a person or thing.
Astronomy. 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. Compare penumbra (def 1a). the dark central portion of a sunspot. Compare penumbra (def 1b).
a phantom or shadowy apparition, as of someone or something not physically present; ghost; spectral image.
a region of complete shadow resulting from the total obstruction of light by an opaque object, esp the shadow cast by the moon onto the earth during a solar eclipse