undershinev.
Etymology: under- prefix1 2a(c).Previous versions of the OED give the stress as: underˈshine.
the world > matter > light > shine [verb (transitive)] > from a specific angle
1844 E. B. Browning 11 A forehead fair and saintly, Which two blue eyes undershine.
This entry has not yet been fully updated (first published 1921; most recently modified version published online June 2019).