secret-codebook
nounUK /ˈsiː.krət ˈkəʊd.bʊk/
US /ˈsiː.krət ˈkoʊd.bʊk/
A secret codebook is a special book that tells you how to read hidden messages.
The spies used a secret-codebook to understand the messages they sent to each other.
RELATED WORDS
OTHER MEANINGS
2. A private list of words or symbols used to hide the meaning of messages.
Only the captain had the secret-codebook for the treasure map.
3. A book that explains a secret language or set of signs.
She found a secret-codebook that showed how to write in pirate symbols.
4. A guide used to turn ordinary words into secret code.
The detective used a secret-codebook to decode the note left at the scene.