The command ‘M-x reverse-region’ will reverse the lines a region. To get the word-based reversal use the command by EvaluatingExpressions or by adding to your InitFile:

  (defun reverse-words (beg end)
    "Reverse the order of words in region."
    (interactive "*r")
        (delete-and-extract-region beg end) "\\b"))))


  first, second, third - last.

Running ‘M-x reverse-words’ on this sentence with the region starting from the beginning but not including the period:

  last - third, second, first.

This has nothing to do with Sorting the words alphabetically. See SortWords.

CategoryEditing CategoryRegion