ajaxurl not defined on front end

I am trying to create a ajaxform on the front side. I am using the code

    jQuery.ajax(
        {
            type: "post",
            dataType: "json",
            url: ajaxurl,
            data: formData,
            success: function(msg){
                console.log(msg);
            }
        });

for which I am getting error

Uncaught ReferenceError: ajaxurl is not definedworklorAjaxBookForm @ 
?page_id=2:291onclick @ ?page_id=2:202

While using similar code on the admin backend works. What url must I use to process the ajax request?