Create a small script which will raise the GNOME Terminal:

echo 'xdotool windowactivate $(xdotool search --onlyvisible --class gnome-terminal)'> ~/raiseterminal.sh && chmod +x ~/raiseterminal.sh

or if you want to check if Terminal is already running, use:

echo -e $'if ps aux | grep "[g]nome-terminal" > /dev/null

 then xdotool windowactivate $(xdotool search --onlyvisible --class gnome-terminal)

 else gnome-terminal &

fi' > ~/raiseterminal.sh && chmod +x ~/raiseterminal.sh

This will create the script ~/raiseterminal.sh with this content:

if ps aux | grep "[g]nome-terminal" > /dev/null                                                                                                                                                                                

 then xdotool windowactivate $(xdotool search --onlyvisible --class gnome-terminal)                                                                                                                                            

 else gnome-terminal&                                                                                                                                                                                                          

fi          

Open the preferences to set up a custom keyboard shortcut and set the command to /home/$USER/raiseterminal.sh, but make sure to change $USER to your actual username.

If you only want to raise the terminal on a specific screen or desktop, see xdotool search --help for more information on how to do this.

There are also various other methods which work better with other window managers.