sulky -
Often derogatory silent and withdrawn after being upset.
Wikipedia
A sulky is a lightweight cart having two wheels and a seat for the driver only but usually without a body, generally pulled by horses or dogs, and is used for harness races. The term is also used for a light stroller, an arch mounted on wheels or crawler tracks and used in logging, or other types of vehicle having wheels and usually a seat for the driver, such as a plough, lister or cultivator.
