To override joomla menu module (whether its left or right or upper one ) you have to copy the following file :

/templates/system/html/modules.php

to your template

/templates/yourtemplate/html/modules.php

and overright the function you want.

ofcourse you can also create your own menu module just you add a function to modules.php

/*
 * Module chrome that wraps the module in a definition list
 */
function modChrome_dlist($module, &$params, &$attribs)
{ ?>
	<dl class="<?php echo $params->get('moduleclass_sfx'); ?>">
	<?php if ($module->showtitle != 0) : ?>
		<dt>
			<?php echo $module->title; ?>
		</dt>
	<?php endif; ?>
		<dd>
			<?php echo $module->content; ?>
		</dd>
	</dl>
	<?php
}
 

then you can add this when calling the menu module

<jdoc:include type="modules" name="left" style="dlist" />

the default styles are :

• table (was 0 and is the default)
• horz (was 1)
• none (was -1)
• xhtml (was -2)
• rounded (was -3)
• outline (new – used to preview module positions – see screenshot above)

was before :

• 0 (the default) displayed modules in a vertical table
• 1 displayed them in a horizontal table
• -1 displayed the raw module output
• -2 displayed the modules in a XHTML compatible format with the title in a H3 tag.
• -3 displayed modules in a set of nested DIVs that allowed for rounded-corner techniques