Un-deploying a list, means you are removing the access of that list in the project folders.
Any list items you might have added at the project folder level, will still be accessible in the Home Folder, once it's been un-deployed.
Steps:
Go to the Home Folder
Click onto the List Library
Select the checkbox of the list you'd like to un-deploy
Click Manage Deployment
Un-select all the folders you wish to remove the list from
Click Apply Changes
Note: If you are un-deploying lists in bulk, click Undeploy & select the folders you wish to remove the list from.
