How do I redirect a taxonomy menu item to another path?
If I understand you want to implement hook_menu_alter() and override the page callback for that path:

function MYMODULE_menu_alter(&amp;$items) {
  $items['taxonomy/term/%taxonomy_term']['page callback'] = 'MYMODULE_taxonomy_page_callback';
}

function MYMODULE_taxonomy_page_callback($term) {
  // Either redirect the page
  drupal_goto('somewhere');

  // Or build up some output to replace the original taxonomy term page.
  // This way you won't actually have to do a redirect at all
}


If I can offer a bit of advice, keep this callback function in your module file so it's always included. Otherwise you'll need to change the file property of the menu item too and that can get quite messy as Drupal is expecting the file to exist in the path that the defining module is in (in this case the taxonomy module).