Syntax: WBADMIN STOP JOB -quiet Description: Cancels the backup or recovery operation that is currently running. Canceled ...

Syntax: WBADMIN STOP JOB [-quiet]

Description:  Cancels the backup or recovery operation that is currently 
running. 
Canceled operations cannot be restarted - you must rerun a canceled backup 
or recovery operation from the beginning.
To use this command, you must be a member of the Backup Operators group 
or Administrators group. 

Parameters:
-quiet         Runs the command with no prompts to the user.