Penumbra

2 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  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]

From WordNet (r) 2.0 [wn]:

  penumbra
       n : a fringe region of partial shadow around an umbra
       [also: {penumbrae} (pl)]