Before you can delete a job in Job Definitions you need to have at least one job created that is in draft status. For more information, see topic Load data with Data Loader.
If there is a data loading job that is not being used and you do not need to use it you have the capability to delete it.
To delete a job :
In the Job Definitions page select Drafts to see the drafts you created.
Select the icon on the right of the date for the job you want to delete.