We found one dictionary that defines the word umbra and penumbra:

Computing (1 matching dictionary)

1. Umbra and Penumbra: Encyclopedia

▸ Words similar to umbra and penumbra ▸ Usage examples for umbra and penumbra ▸ Idioms related to umbra and penumbra ▸ Wikipedia articles (New!) ▸ Words that often appear near umbra and penumbra ▸ Rhymes of umbra and penumbra ▸ Invented words related to umbra and penumbra