umbra

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A dark area, especially the blackest part of a shadow from which all light is cut off. See Synonyms at shade.
2. n. Astronomy The completely dark portion of the shadow cast by the earth, moon, or other body during an eclipse.
3. n. Astronomy The darkest region of a sunspot.

Century Dictionary and Cyclopedia

1. n. A shadow or shade. Specifically, in astronomy: The total shadow of the earth or moon in an eclipse; the dark cone projected from a planet or satellite on the side opposite to the sun. See penumbra (with cut).
2. n. Among the Romans, one who went to a feast merely at the solicitation of one invited: so called because he followed the guest as a shadow.
3. n. In algebra, a symbol which, when paired with another, makes the symbol of a quantity. See umbral notation, under umbral.
4. n. The only genus of Umbridæ; the mud-minnows. See minnow. 2 , and Umbridæ. There are two species, respectively of Europe and North America, U. krameri and U. limi.
5. n. [lowercase] A sciænoid fish, Umbrina cirrosa; the umbrine. See cut under Umbrina.

Wiktionary

1. n. A shadow.
2. n. astronomy The central region of a sunspot.

GNU Webster's 1913

1. n. The conical shadow projected from a planet or satellite, on the side opposite to the sun, within which a spectator could see no portion of the sun's disk; -- used in contradistinction from penumbra. See penumbra.
2. n. The central dark portion, or nucleus, of a sun spot.
3. n. The fainter part of a sun spot; -- now more commonly called penumbra.
4. n. (Zoöl.) Any one of several species of sciænoid food fishes of the genus Umbrina, especially the Mediterranean species (Umbrina cirrhosa), which is highly esteemed as a market fish; -- called also ombre, and umbrine.

WordNet 3.0

1. n. a region of complete shadow resulting from total obstruction of light