User shows up in people picker after being deleted from Active Directory

If a user has ever accessed a sharepoint site or had been added to a sharepoint site, he/she will keep appearing in the people picker after the user has been deleted from the corresponding active directory because of termination/name change/???. To correct the people picker, follow these simple steps:

• Go to Site Setting -> People and Groups
• In "All People", filter on the user name that was deleted from AD.
• Select the user and choose Delete users from site collection under the Actions menu

This will remove the user from the people picker.