The axis title, showing next to the axis line.

Option name	Type	Default
align	String	"middle"
Alignment of the title relative to the axis values. Possible values are "low", "middle" or "high".
margin	Number
The pixel distance between the axis labels or line and the title. Defaults to 0 for horizontal axes, 10 for vertical
rotation	Number
The rotation of the text in degrees. 0 is horizontal, 270 is vertical reading from bottom to top. Defaults to 0.
style	Array
CSS styles for the title. When titles are rotated they are rendered using vector graphic techniques and not all styles are applicable. Most noteworthy, a bug in IE8 renders all rotated strings bold and italic.
text	String	null
The actual text of the axis title. It can contain basic HTML text markup like b, i and spans with style.