penumbral

[ pi-nuhm-bruhl ]

Phonetic (Standard)IPA

adjective

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.
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.
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.

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