Setting the title text to an empty string is the way to do it.
No space is created for the title in that case:
without text: http://jsfiddle.net/jlbriggs/JVNjs/284/
with text: http://jsfiddle.net/jlbriggs/JVNjs/286/
title:{
text:''
}
If you want less space than is left in that case, simply set your ‘marginTop’ to 0
{{edit due to numerous comments:
As pointed out a number of times below, the documentation now states text: null as the method to achieve this.
Either method achieves the desired result.