- a shadowy, indefinite, or marginal area.
Origin of penumbra
1660–70; < New Latin, equivalent to Latin paen- pen- + umbra shade
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for penumbral
The line between the real and imaginary is vague and penumbral to us.Hills and the Sea
It may be that all the elements of the penumbral cone intersect the earth.
Isabel snuck into the guest bedroom and settled into an overstuffed armchair at a penumbral corner.The Capgras Shift
Strange, penumbral, characters roam the boardrooms of banks in the countries in transition.After the Rain
The penumbral line is marked from hour to hour on the maps given annually in the American Ephemeris.
- a fringe region of half shadow resulting from the partial obstruction of light by an opaque object
- astronomy the lighter and outer region of a sunspot
- painting the point or area in which light and shade blend
C17: via New Latin from Latin paene almost + umbra shadow
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for penumbral
1660s, from Modern Latin penumbra "partial shadow outside the complete shadow of an eclipse," coined 1604 by Kepler from Latin pæne "almost" + umbra "shadow" (see umbrage). Related: Penumbral.
Online Etymology Dictionary, © 2010 Douglas Harper
- A partial shadow between regions of full shadow (the umbra) and full illumination, especially as cast by Earth, the Moon, or another body during an eclipse. During a partial lunar eclipse, a portion of the Moon's disk remains within the penumbra of Earth's shadow while the rest is darkened by the umbra. See Note at eclipse.
- The grayish outer part of a sunspot. Compare umbra.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.