penumbral

[ pi-nuhm-bruhl ]

adjective

1. Astronomy.
   1. of, causing, or being the partial shadow outside the complete shadow of an opaque body, such as a planet, where the light from the source of illumination is only partly cut off: Compare umbral 2a.

      Four consecutive total lunar eclipses in a row, without any penumbral eclipses in between, are known as a tetrad.

   2. relating to or being the grayish marginal portion of a sunspot: Compare umbral 2b.

      An average eye can see a sunspot with a penumbral diameter of at least 41 arcseconds.

2. relating to or being a shadowy, indefinite, or marginal area:

   The apple trees provide penumbral lighting that is perfect for studying, thinking, or even a nap.

   While the beneficiaries of corruption fête themselves with cocktail nights and caviar dreams, its victims wander a penumbral existence.

3. U.S. Law. of or relating to the set of rights implicit in the U.S. Constitution or Bill of Rights:

   The wealthy, like everyone else, are entitled to the full enjoyment of the Constitution's express and penumbral guarantees.

Word History and Origins

Origin of penumbral¹

penumbra ( def ) + -al ¹( def )

Example Sentences

As the moon prepares to blot out the surface of our sun in two weeks, it’s warming up with a penumbral lunar eclipse on Sunday night or Monday morning, depending on your time zone.

From New York Times

In what’s known as a penumbral lunar eclipse, the full moon passed within the outer part of Earth’s shadow, causing the moon to dim only slightly.

From Seattle Times

Compositionally, this shot of a narrow, penumbral domestic space is a stunner.

From New York Times

The total lunar eclipse will begin as an unremarkable “penumbral” lunar eclipse — a subtle darkening hardly perceptible to the untrained observer.

From Washington Post

Or we can stay exactly where we are, in this state of gorgeous make-believe, this penumbral present, with its rich colors, heavy drapes and musty air of perfume, popcorn and potential.

From Washington Post