The RadMenu allows you to specify delays for its closing and opening actions. This means that you can make the RadMenu wait for a specific amount of time before opening or closing a menu. In order to specify these delays you can set the ShowDelay and HideDelay properties. They are of type Duration and have the following format in XAML "0:0:0.00".
Note that when the ClickToOpen property is set to True, the delays don't affect the RadMenu's behavior.
Here is an example of a RadMenu with a delay before opening a menu equal to one second and a delay before closing a menu also equal to one second.
<telerik:RadMenu VerticalAlignment="Top" ShowDelay="0:0:1" HideDelay="0:0:1"> ... </telerik:RadMenu>