Shifts all lines in the selection to the previous tab stop. If you place the cursor anywhere in a line and choose the Outdent command, the entire line is shifted to the previous tab stop. All lines in the selection are moved the same number of spaces to retain the same relative indentation within the selected block.

You can change the tab width on the Editor tab of the Options dialog box.

Toolbar shortcut: toolbar button. Keyboard shortcuts: CTRL+SHIFT+M.