Emily Dickinson Lexicon

PE-NUM'BRA, n. [L. pene, almost, and umbra, shade.]

1. In astronomy, a partial shade or obscurity on the margin of the perfect shade in an eclipse, or between the perfect shade, where the light is entirely intercepted, and the full light. – Cyc.
2. In painting, the point of a picture where the shade blends with the light. – Elmes.