Is “Umbra” a Scrabble word?
Yes
UMBRA
Valid in at least one Scrabble dictionary
Valid in these dictionaries
SOWPODS / CSW
Scrabble UK & International
TWL / NWL
Scrabble North America
Large English Dictionary
General English word list
Meaning of Umbra
/ˈʌmbɹə/
noun
1.The fully shaded inner region of a shadow cast by an opaque object.
2.The central region of a sunspot.
3.A shadow.