This question relates to https://drupal.stackexchange.com/questions/25613

I followed the recommendations of Clive and wrote a hook_menu_alter to provide my callback. 

    function material_menu_taxonomy_page_callback($term) {
      dsm('Entered material menu callback');
    }

    function material_menu_menu_alter () {
      $items['taxonomy/term/%taxonomy_term']['page callback'] = 'material_menu_taxonomy_page_callback'; 
    }

I placed a code line `dsm("Altering");` in the callback to see where in the process the callback is being called, but it never shows up.

I am fairly certain that I have the code correct. 

 - The hook has the name of the custom module. 
 - The callback name is correct.  
 - the callback is in the same file as the hook
 - I have turned the module off and then on so that I can be sure that Drupal knows about `mymodule_menu_alter` 
 - And I have flushed the caches.

My assumption is that `mymodule_menu_alter()' should change the callback in the menu item array and that the callback will be called each time the menu item is selected. That suggests that my `dsm()` message should display at the top of the page requested by the menu. 

While Clive's test indicated in his answer worked, my revisions did not. Following Clive's answer recommendations I revised the code as follows.

### material.info file contained in modules subdirectory = sites/all/modules/Custom/material

<!-- language: lang-none -->

    name = Materials  
    description = Redefine the path for materials menu
    package = CR-Hub
    core = 7.x
    ; Includes
    files[] = material.module

### material.module file in same subdirectory

    function material_taxonomy_page_callback() {
      drupal_goto('taxonomy/term/1');
      // return 'Entered material menu callback';
    }

    function material_menu_alter(&$items) {
      // return 'Entered Material Menu Alter';
      $items['taxonomy/term/%taxonomy_term']['page callback'] = 'material_taxonomy_page_callback'; 
      return $items;
    }

When I select any menu item neither `drupal_goto()`, or `return 'any text'` lines redirect the selected path from the menu item.