This code can help you :
$(document).ready(function() {
$('#calendar').fullCalendar({
events:
[
{
id: 1,
title: 'First Event',
start: ...,
end: ...,
description: 'first description'
},
{
id: 2,
title: 'Second Event',
start: ...,
end: ...,
description: 'second description'
}
],
eventRender: function(event, element) {
element.find('.fc-title').append("<br/>" + event.description);
}
});
}