A process stops responding normally. When you try to exit it using Ctrl C, it prints
^C instead. Whatever you type just prints on the screen, the process seems to be stuck, and you hate restarting a new instance of the terminal.
Try Ctrl \
If that doesn't help, send the process of the background using Ctrl Z. Then bring it back:
If even that doesn't help, send it to the background again, and:
$ kill $!
There you have you terminal free again. No more closing of the terminal instance because of a frozen process. Happy hacking!