Wiktionary
n. 1 A shell, a command line interface; (non-gloss definition: usually used with the definite article.) 2 (context computing English) The text prompt presented to the user in a command line interface. 3 A line of text that is entered at such a prompt.
WordNet
n. commands that a user types in in order to run an application
Usage examples of "command line".
When working with something as powerful as Linux, you can easily devote a full half-hour to engineering a single command line.
Many don't have a GUI at all, and many that do are capable of running from the command line.
Of course, since my computer only has one monitor screen, I can only see one command line, and so you might think that I could only interact with one program at a time.
The command line interface makes it easy for programs to dribble out little comments, warnings, and messages here and there.
No, the way to gain a towering reputation on the Internet would be to get so good at tweaking your command line that your universes would spontaneously develop life.
This way of doing it did not even have a name at the time, but when, much later, an alternative became available, it was retroactively dubbed the Command Line Interface.
It was, in other words, a glass teletype running a command line interface.
It was not until a few years later, when I began messing around with Unix, that I understood that the command line interface embodied in MPW was a re-creation of Unix.
In other words, the command line interface is available if you want it.