After installing WordPress you will find an uncategorized category which you would like to rename or delete it.
How to delete uncategorized category from WordPress
Step 1 : Go to your WordPress dashboard==>Settings==>Writing==>Default post category then change it to different category in my case i have set it to linetoweb and then click on save changes.
Step 2 : Click on posts==>Categories==>Select uncategorized category and click on delete.
Congratulation you have deleted the default uncategorized category from your WordPress blog.