penumbral

pe·num·bra  (p-nmbr)

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

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

2. The grayish 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 pnumbra : Latin paene, almost + Latin umbra, shadow.]

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pe·numbral, pe·numbrous adj.

Thesaurus

Adj.

1.

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