Up until now, it's not possible to 'completely' delete your Facebook account. The only option you have is to 'Deactivate Account' which means that your account will remain dormant with all your information until next time you visit and re-activate it. Although your account is in dormancy, people will still be able to send you messages if they wanted, only that you won't be receiving them until the day you sign in again.

News reports are out there suggesting that Facebook is testing the 'Deactivate or Delete Account' feature.

This feature is rolled out to only a few Facebook users (I don't have it) but what will be the outcome of it? we shall have to wait until further notice.

For the time being though, if for some reasons you decide you want to permanently delete your Facebook account, you have to do some tweaking by reading tips and tricks online on "how to delete facebook account permanently", and when you have successfully employed those instructions, you have to wait for 14 days for it to be wiped off the database (?). Note that, during this waiting period, you have to adhere to not login in or in anyway accessing your 'to be deleted facebook account', short of which, you will have to start the whole process afresh.