Where are you seeing this supposed variable?
If it is under variables by pressing the bottom left hand 'x=' icon, then it was created by someone in your development group and the definition would be there.
If it was created in the ETL, you will need to run a search on the pages using Data Load Editor.
If you don't have access to the Data Load Editor, you will need to speak to your admin, he/she should have the definition.
