array key: bulk_actions
array value: array(bulk action key and name => bulk action dropdown value)
The bulk_actions array populates the bulk actions dropdown with the array key becoming the option value and the array value becoming the corresponding dropdown display value. The list table bulk action dropdown name is action for the top and action2 for the bottom, which both should be retrieved from the query string when processing the bulk action.
$list_table_definitions['bulk_actions'] = isset($_GET['status']) && ($_GET['status'] == "trash") ? array( 'bulk_delete' => 'Delete' ) : array( 'bulk_trash' => 'Trash' );