Keyboard command/shortcut to resize window

The bottom of my (Chromium) window is off the bottom of the screen. If I move the window up, Unity maximises the window (which I do not want).

What key combination can I press to make the active window shorter (smaller)?

Hold down Alt and press space.

Then press R on your keyboard. You can now use the arrows to resize the window.

You can press Alt + F8 and your mouse pointer will automatically switch to a resizing pointer, which you can use to resize your window either with the mouse or using the arrow keys.

You can then click or press esc to stop and turn your normal pointer back on.