\Pe*num"bra\, n. [NL., fr. L. paene almost + umbra
shade.]
1. An incomplete or partial shadow.
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.
Note: The faint shade surrounding the dark central portion of
      a solar spot is also called the {penumbra}, and
      sometimes {umbra}.
3. (Paint.) The part of a picture where the shade
   imperceptibly blends with the light.