Akademik

monoalphabetic substitution
\\| ̷ ̷ ̷ ̷ at mono-+-\ noun
Etymology: mon- + alphabetic
: substitution in cryptography that uses a single substitution alphabet so that each plaintext letter always has the same cipher equivalent — compare polyalphabetic

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/mon"oh al'feuh bet"ik, mon'oh-/, Cryptography.
a system of substitution that uses only one cipher alphabet in a cryptogram so that each plaintext letter is always represented by the same cipher. Cf. polyalphabetic substitution.
[1935-40; MONO- + ALPHABETIC]

Useful english dictionary. 2012.