The adjective terminated refers to something that's been brought to an end, often abruptly. If you sister hangs up on you in the middle of a conversation, you can describe your phone call as terminated.
Anything canceled or concluded is terminated. At work, a terminated employee is one who's been fired, and legally a terminated contract has reached the end of its official term or been declared void. Terminated has its roots in the Latin word terminus, "end or limit."