Is “Lengthiest” a Scrabble word?
Yes
LENGTHIEST
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 Lengthiest
adjective
1.Having length; long and overextended, especially in time rather than dimension.
“She died last night after a lengthy illness.”
2.Speaking or writing at length; long-winded.