Ubuntu – How to disable Ctrl+Alt+s to minimize a window

1. Go to System settings... -> Keyboard Layout -> Options...,
2. unwind Miscellaneous compatibility options,
3. check Special keys (Ctrl+Alt+<key>) handled in a server.

Please, be aware it will also disable some other shortcuts (e.g. ctrl+alt++ and ctrl+alt+- used to switch video modes).

On current Ubuntu metacity is no longer the default window manager, so the accepted solution no longer works. Instead there's a different setting that you can change. Set the key combination to an empty array.

In a terminal:

gsettings set org.gnome.settings-daemon.plugins.media-keys terminal '[]'

To undo the change again

gsettings reset org.gnome.settings-daemon.plugins.media-keys terminal 

In case this changes again, I found this by looking for all settings that mention "terminal"

gsettings list-recursively | grep terminal

I had this problem because it interferes with an Emacs keybinding to transpose sexps.