Is “Jackknifing” a Scrabble word?
Yes
JACKKNIFING
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 Jackknifing
verb
1.To fold in the middle, as a jackknife does.
“The cat jackknifed in the air and landed gracefully on its feet.”
2.To cause a semi-trailer truck to fold like a jackknife in a traffic accident.
“Before I knew what was happening, I'd jack-knifed the truck.”