mon|o|al|pha|bet|ic «MON oh AL fuh BEHT ihk», adjective.
Cryptography. having to do with or using a single cipher alphabet: »
the ancient cryptographic technique of monoalphabetic substitution, in which only one letter is substituted for another to encipher a message (Scientific American).
Also, monalphabetic.–mon´o|al´pha|bet´i|cal|ly, adverb.
Useful english dictionary. 2012.