[plugin: menubar] jQuery is not defined

I’m using menubar on a site and it’s not displaying properly. The test site is here: http://test.timlepczyk.com/

Debugging in Chrome, I see the the error: “Uncaught ReferenceError: jQuery is not defined” but the script uses the code listed in the codex.

<script type="text/javascript">
// <![CDATA[
jQuery(document).ready(function($) {
$("ul.ssf-yellow").superfish ({
    hoverClass:    "wpm-hover",
    delay:         500,
    animation:     {opacity:"show"},
    speed:         "slow",
    autoArrows:    true,
    dropShadows:   true,
    disableHI:     true
});
});
// ]]>
</script>

What do I need to fix?