Definition of "penumbra" [pe•num•bra]

• A partial shadow, as in an eclipse, between regions of complete shadow and complete illumination. See Synonyms at shade. (noun)
• The grayish outer part of a sunspot. (noun)
• An area in which something exists to a lesser or uncertain degree: "The First Amendment has a penumbra where privacy is protected from governmental intrusion” ( Joseph A. Califano, Jr.) (noun)
• An outlying surrounding region; a periphery: "Downtown Chicago and its penumbra also stand rejuvenated” ( John McCormick). (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "And a penumbra is a different kettle of fish entirely – the metaphor was used by Justice Douglas in Griswold v. Connecticut and partakes more of substantive due process than anything else."
• "And a penumbra is a different kettle of fish entirely–the metaphor was used by Justice Douglas in Griswold v."
• "A penumbra is the partial shadow cast onto one celestial body (e.g., the Earth) when another celestial body (e.g., the Moon) partically but not completely occludes light from a source (e.g., the Sun)."