Is “Jack” a Scrabble word?
Yes
JACK
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 Jack
/dʒæk/
noun
1.A coarse mediaeval coat of defence, especially one made of leather.