penumbra

2 definitions found

penumbra - Collaborative International Dictionary of English v.0.48 :

  Penumbra \Pe*num"bra\, n. [NL., fr. L. paene almost + umbra
     shade.]
     1. An incomplete or partial shadow.
        [1913 Webster]
  
     2. (Astron.) The shadow cast, in an eclipse, where the light
        is partly, but not wholly, cut off by the intervening
        body; the space of partial illumination between the umbra,
        or perfect shadow, on all sides, and the full light. --Sir
        I. Newton.
        [1913 Webster]
  
     Note: The faint shade surrounding the dark central portion of
           a solar spot is also called the penumbra, and
           sometimes umbra.
           [1913 Webster]
  
     3. (Paint.) The part of a picture where the shade
        imperceptibly blends with the light.
        [1913 Webster]

penumbra - WordNet (r) 2.1 (2005) :

  penumbra
      n 1: a fringe region of partial shadow around an umbra