Crescent

The shape you get if you cut out of a circle another circle of roughly the same size, but offset to one side. You might also describe it as the shape the lit side of a sphere takes on if, in respect to the viewer, the light source is behind and to one side of the sphere (as in a crescent moon).

    _________
      \__    \____
         \__      \_
            \_      \_
              \       \
               \       \
                |       \
                |        |
                 |       |
                 |       |
                |        |
                |       /
               /       /
             _/      _/
          __/      _/
       __/    ____/
    __/______/