The visible() method, called without any parameters, will return the current visibility state of the tooltip element.
The visible(boolVisible, target) method is used to make the tooltip visible/invisible for the given target element.

<div id="container">Hello World!</div>

<script type="text/javascript">
    $(function () {
        var tooltip = $("#container").shieldTooltip({
            content: "Hello world tooltip!"

        tooltip.visible(); // returns true

        tooltip.visible(false, $('#container')) // makes the tooltip invisible for the container div element.

        tooltip.visible(); // returns false