What is the ellipsis badge on minimized terminal app in the dock mean?
See the question Terminal doesn't show badge - how to enable?. In the accepted answer it says:


  There is also an "unread text" indicator displayed in tabs, in the
  form of ellipsis ("…"):
  
  This is displayed when anything is written to a background terminal, and, like the bell indicator, cleared when you activate that
  terminal window/tab. An "unread text" ellipsis is also displayed on
  minimized terminal windows in the Dock.