Sure you can, just create your own toggle functionality
$(".thumnails").on("mouseover mouseout", "a", function () {
var flag = $(this).data('flag');
$('[title="' + $(this).attr('href') + '"]').css('visibility', flag ? 'hidden' : 'visible');
$(this).data('flag', !flag);
});
or split the events
$(".thumnails").on({
mouseover: function() {
$('[title="' + $(this).attr('href') + '"]').css('visibility', 'visible');
},
mouseout: function () {
$('[title="' + $(this).attr('href') + '"]').css('visibility', 'hidden');
}
}, 'a');