cipher – secret code; a secret way of writing
(Pronounced sigh-fur)
To remember the definition of the word cipher, use the following mnemonic:
On the side of the bear's furry (cipher) body was a secret code.

Examples of cipher in a sentence
She developed a secret cipher to write her diary in so that if anyone ever tried to read it, it would look like a jumble of letters.
Banks and credit card companies use a cipher to disguise card information and make it harder to steal information.
The serial killer left a cipher with each body that provided clues to the detectives on where to find the next victim.