Ctrl+Alt+t is the keyboard shortcut to open a terminal in Ubuntu. By default, it opens an ‘x-terminal-emulator’ terminal.

I wanted to change that to use my favorite terminal emulator, which is ‘terminator’

To do that:

gsettings set org.gnome.desktop.default-applications.terminal exec 'terminator'

or:

sudo update-alternatives --config x-terminal-emulator

That’s it!

Enjoy!

Source:

https://askubuntu.com/questions/70540/how-can-i-set-default-terminal-used-in-unity