How to Delete an Old Twitter Profileby C. Taylor
If you need only to remove old profile data from your primary account, you can click the gear icon and select "Edit Profile" to access the data. Simply entering new data and then clicking "Save Changes" will remove the information. However, if you no longer use Twitter, you have the option of deleting your entire account, including your profile information.
Deactivating Your Account
To deactivate your account, you must log in through the standard website; this option is not available through mobile devices. If you forgot your password for your old account, visit the password recovery page and enter your details (link in Resources). Clicking the gear icon from your account, selecting "Settings" and then choosing "Deactivate My Account" starts the deactivation process. Once deactivated, Twitter gives you 30 days to reactivate the account. If you don't reactivate the account in that time, all your data is permanently removed.