special-purpose code

noun
UK /ˈspeʃəl ˈpɜːpəs kəʊd/
US /ˈspeʃəl ˈpɜːrpəs koʊd/

A special-purpose code is a set of secret symbols made just for one job.

The spy used a special-purpose code to send a message that only her team could read.


OTHER MEANINGS

2. A computer program written to do one particular task instead of many.

The engineer wrote a special-purpose code to sort the school's test scores.

3. A short set of letters or numbers used only for a single kind of product or activity.

Each library book has a special-purpose code that shows which shelf it belongs on.

4. A private set of rules for writing messages that only certain people understand.

The club members made a special-purpose code so their meeting notes stayed secret.