Designation in the personal data
In general, it can mean one of two things:


Your title. For example, Dr., Rev., Arch., Atty., Engr., etc.
Your job title. For example, Head of Gastrointestinal Surgery, Parish Priest, Associate Professor of Global Health, etc.


It really depends on the place in the application in which the information is being sought and for what use.

Anyway, good luck!