Definition of penumbra
- penumbra Noun A partially shaded area around the edges of a shadow, especially an eclipse.
- penumbra Noun A region around the edge of a sunspot, darker than the sun's surface but lighter than the middle of the sunspot.
- penumbra Noun Something related to, connected to, and implied by, the existence of something else that is necessary for the second thing to be full and complete in its essential aspects.
- penumbra Noun (in ischaemic penumbra", after a stroke)" A region of the brain that has lost only some of its blood supply, and retains structural integrity but has lost function.