Is “Codebook” a Scrabble word?
Yes
CODEBOOK
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 Codebook
noun
1.A book, table, database, or other object that stores the mapping between plaintext words or phrases and their equivalents in a code.
2.A lookup table.