Definition from Wiktionary, the free dictionary
Alternative forms 
- cypher, less common than cipher but still in use in English. see The Ultra Secret by Winterbotham, the cypherpunk movement, and consider the Royal Navy's series of Cyphers (Nr 1, Nr 2, Nr 3, ...) before and into WWII.
cipher (plural ciphers)
- A numeric character.
- A method of transforming a text in order to conceal its meaning.
- The message was written in a simple cipher. Anyone could figure it out.
- (cryptography) A cryptographic system using an algorithm that converts letters or sequences of bits into ciphertext.
- Ciphertext; a message concealed via a cipher.
- The message is clearly a cipher, but I can't figure it out.
- A grouping of three digits in a number, especially when delimited by commas or periods:
- The probability is 1 in 1,000,000,000,000,000 — a number having five ciphers of zeros.
- A design of interlacing initials: a decorative design consisting of a set of interlaced initials.
- (music) A fault in an organ valve which causes a pipe to sound continuously without the key having been pressed.
- A hip-hop jam session 
- The path (usually circular) shared cannabis takes through a group, an occasion of cannabis smoking.
- Someone or something of no importance.
- You are just a cipher to me.
- (obsolete) Zero.
- (numeric character): number, numeral
- (method for concealing the meaning of text): code
- (cryptographic system using an algorithm):
- (a grouping of three digits in a number, especially when delimited):
- (design of interlacing initials): monogram
- (fault in an organ valve causing a pipe to sound continuously):
- (hip-hop jam session):
- (path that shared cannabis takes through a group):
- (someone or something of no importance): (person): nobody, nonentity; (thing) nonentity, nothing, nullity
- (obsolete: zero): naught/nought, nothing, oh, zero
Derived terms 
Related terms 
method for concealing the meaning of text
cryptographic system using an algorithm
design of interlacing initials
fault in an organ valve causing a pipe to sound continuously
hip-hop jam session
path that shared cannabis takes through a group
someone or something of no importance
- (regional and/or dated) To calculate.
- I never learned much more than how to read and cipher.