JQuery :: FAQ Show / Hide Function - If Statement

I have a simple FAQ show/hide function set up however I am having trouble setting up an if clause. My code is:
$(document).ready(function(){
$("dd").hide();
$("dt").click(function(){
$("dd").hide('slow');
$(this).next().slideToggle();
});
});

However, when you click on the same item twice it firstly hides and then reshows it, I need an if statement that basically states;
if "this?!" is visible/shown
Then do nothing
else
$("dd").hide('slow');
$(this).next().slideToggle();
I am unsure of the syntax and can't figure out what property I can trace out to see if the item is being shown or not.