title_body: Is there a specific term for a substitution cipher language? A really simple but effective method to create an unintelligble language from a given language is applying a substitution cipher to the vocabulary. In order to be pronouncable, vowels should be substituted with vowels, and consonants with other consonant of comparable sonority.
  
  It is of course a special case of a relexification, but is there a specific term for this?
upvoted_answer: "code" or "coded language". Probably mostly used in conjunction with sign languages, where the signs replace the (spoken) words (e.g. Signing Exact English as opposed to "natural" signed languages), but also for "encoded" spoken languages (either by relexification or phoneme substitution).