Is “Circumvallation” a Scrabble word?
Yes
CIRCUMVALLATION
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 Circumvallation
/sɜːkəmvæˈleɪʃən/
noun
1.A rampart or other defensive entrenchment that entirely encircles the position being defended.