penumbra |peˈnəmbrə| noun (pl. penumbrae |-brē, -brī| or penumbras) the partially shaded outer region of the shadow cast by an opaque object.• Astronomy the shadow cast by the earth or moon over an area experiencing a partial eclipse.• Astronomy the less dark outer part of a sunspot, surrounding the dark core.DERIVATIVES penumbral |-brəl| adjectiveORIGIN mid 17th cent.: modern Latin, from Latinpaene ‘almost’ + umbra ‘shadow.’
Not all shadows are created equal.