Answer to Stack Overflow question http://stackoverflow.com/questions/38024236/highcharts-xaxis-label-with-linefeed-how-to-make-smaller-gap

author(s): Mike Zavarello

HTML

<script src="https://code.highcharts.com/highcharts.js"></script>

<div id="container" style="height: 400px"></div>

JavaScript

$(function () {
    $('#container').highcharts({

        tooltip: {
            formatter: function () {
                return 'The value for <b>' + this.x +
                    '</b> is <b>' + this.y + '</b>';
            }
        },

        xAxis: {
            categories: ['Jan<', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'], 
            labels: {
            	useHTML: true,
              style: {
                lineHeight: '200%'
              }
            }
        },

        series: [{
            data: [29.9, 71.5, 106.4, 129.2, 144.0, 176.0, 135.6, 148.5, 216.4, 194.1, 95.6, 54.4]
        }, {
            data: [194.1, 95.6, 54.4, 29.9, 71.5, 106.4, 129.2, 144.0, 176.0, 135.6, 148.5, 216.4]
        }]
    });
});