Picklist is an element attribute which allows to define a list of possible values for that element. Of course it must be a measure dimension element in order a picklist to work.
To define a picklist you need to add “Picklist” string attribute to your dimension and for the required element set it to one of the following:
1). Static values:
If you delete an option in your picklist, that values will remain in all cube cells where it is selected. You have to re-enter / re-select the value if you want to reflect the changes you made to the pick list.