Dynamic title provided by Block/Result.php in catalogsearch module. So you have to override the Block/Result.php into your local folder. There you can change the title as per your requirement.
app/code/local/Mage/CatalogSearch/Block/Result.php
Your local file path should be like this.
class Mage_CatalogSearch_Block_Result extends Mage_Core_Block_Template
{
/**
* Catalog Product collection
*
* @var Mage_CatalogSearch_Model_Resource_Fulltext_Collection
*/
protected $_productCollection;
/**
* Prepare layout
*
* @return Mage_CatalogSearch_Block_Result
*/
protected function _prepareLayout()
{
// add Home breadcrumb
$breadcrumbs = $this->getLayout()->getBlock('breadcrumbs');
if ($breadcrumbs) {
$title = $this->__("Search results for: '%s'", $this->helper('catalogsearch')->getQueryText());
$breadcrumbs->addCrumb('home', array(
'label' => $this->__('Home'),
'title' => $this->__('Go to Home Page'),
'link' => Mage::getBaseUrl()
))->addCrumb('search', array(
'label' => $title,
'title' => $title
));
}
// modify page title
$title = $this->__("shopping with ('%s')", $this->helper('catalogsearch')->getEscapedQueryText());
$this->getLayout()->getBlock('head')->setTitle($title);
return parent::_prepareLayout();
}
}