The Free On-line Dictionary of Computing (30 December 2018):

terminal emulator

    A program that allows a computer to act like
   a (particular brand of) terminal, e.g. a vt-100.  The
   computer thus appears as a terminal to the host computer and
   accepts the same escape sequences for functions such as
   cursor positioning and clearing the screen.

   xterm is a terminal emulator for the X Window System.

   (1995-02-16)