penumbral

penumbra

pe·num·bra

 (pĭ-nŭm′brə)

n. pl. pe·num·bras or pe·num·brae (-brē)

1. A partial shadow, as in an eclipse, between regions of complete shadow and complete illumination.

2. The diffuse outer part of a sunspot.

3. An area in which something exists to a lesser or uncertain degree: "The First Amendment has a penumbra where privacy is protected from governmental intrusion" (Joseph A. Califano, Jr.).

4. An outlying surrounding region; a periphery: "Downtown Chicago and its penumbra also stand rejuvenated" (John McCormick).

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[New Latin pēnumbra : Latin paene, almost + Latin umbra, shadow.]

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pe·num′bral, pe·num′brous adj.

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Thesaurus

Adj.

1.

penumbral - of or pertaining to the region of partial shadow around an umbra

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