UID - a name or number used to identify a specific individual user when accessing a remote system - often has to be followed by a password
Found on http://www.archivemag.co.uk/
This is the account reference name sent to you in the Account Activation Letter. When you need to log on to your site, you will use this item. A User ID is sometimes referred to as a 'user name'.
Found on http://www.encyclo.co.uk/local/20660
a unique identifier selected by a person opening an account. At WebCom, you can potentially have two different User IDs. One for your WebCom service plan and one for your WebCommerce store. Found on https://www.encyclo.co.uk/local/21088