"Unused credit" refers to the portion of credit that you have been approved for but have not used or spent yet. It is the available credit you still have remaining on your account. Full definition
For these reasons, do not close unused credit card accounts or open new credit card accounts just in hopes of raising your credit score because these actions may actually lower your score. (badcreditloanservices.com)
Paying off loans, closing unused credit card accounts, and making regular payments on credit cards and other loans will help. (abcloanguide.com)
This is also a good time to close a couple of unused credit card accounts. (abcloanguide.com)