The Collaborative International Dictionary
job control language \job control language\ (Computers) A programming language used to specify the manner, timing, and other requirements of execution of a task or set of tasks submitted for execution, especially in background, on a multitasking computer; a programming language for controlling job[7] execution. Abbreviated JCL.
Wikipedia
Job Control Language (JCL) is a name for scripting languages used on IBM mainframe operating systems to instruct the system on how to run a batch job or start a subsystem.
There are two distinct job control languages: one for the operating system lineage that begins with DOS/360 and whose latest member is z/VSE; and the other for the lineage from OS/360 to z/OS. They share some basic syntax rules and a few basic concepts, but are otherwise very different.
Other mainframe batch systems had some form of job control language, whether called that or not; their syntax was totally different from IBM versions, but they usually provided similar capabilities. Interactive systems include " command languages"—command files (such as PCDOS ".bat" files) can be run non-interactively, but these usually do not provide as robust an environment for running unattended jobs as JCL. On some computer systems the job control language and the interactive command language may be different. For example, TSO on z/OS systems uses CLIST or Rexx as command languages along with JCL for batch work. On other systems these may be the same.