I am a bit confused on the new bootstrap version since they changed dropdown menus to divs:
Andrei's "complete" jQuery+CSS solution has the right intent, but it's verbose and still incomplete. Incomplete because while it probably covers all the necessary DOM changes, it's missing the firing of custom events. Verbose because it's wheel-reinventing when Bootstrap already provides the dropdown() method, which does everything.
So the correct, DRY solution, which does not rely on the CSS hack often repeated among other answers, is just jQuery:
$('body').on('mouseover mouseout', '.dropdown', function(e) {
$(e.target).dropdown('toggle');
});