[ pi-nuhm-bruhl ]

  1. Astronomy.

    • 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:Four consecutive total lunar eclipses in a row, without any penumbral eclipses in between, are known as a tetrad.: Compare umbral 2a.

    • relating to or being the grayish marginal portion of a sunspot:An average eye can see a sunspot with a penumbral diameter of at least 41 arcseconds.: Compare umbral 2b.

  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.

  1. 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.

Origin of penumbral

  • Sometimes pe·num·brous [pi-nuhm-bruhs] /pɪˈnʌm brəs/ .

Words Nearby penumbral Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use penumbral in a sentence