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

The penumbral line is marked from hour to hour on the maps given annually in the American Ephemeris.

From Project Gutenberg

I think the intellect, when focussed so as to give definition without penumbral haze, is sure to realise this image at the last.

From Project Gutenberg

Strange, penumbral, characters roam the boardrooms of banks in the countries in transition.

From Project Gutenberg

Isabel snuck into the guest bedroom and settled into an overstuffed armchair at a penumbral corner.

From Project Gutenberg

It may be that all the elements of the penumbral cone intersect the earth.

From Project Gutenberg