Meaning of “shadow” - Learner’s Dictionary

shadow

noun [ C, U ] us uk /ˈʃædəʊ/
A figure emerged from the shadows.Someone was lurking in the shadows.His face was obscured by a shadow.The shadow of the tower fell across the lawn.The dog was chasing its own shadow.

B1 a dark area made by something that is stopping the light:

The tree had cast / (= made) a long shadow.

(Definition of “shadow noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)