Gesture drawing, also called gestural drawing, is an expressive, intuitive drawing based on a close and thoughtful observation of the subject in space. Gesture drawing attempts to capture the essence of form and movement. Its especially used in figure drawing, where it encourages you to observe the whole figure and get a sense of the dynamism of the human form, but you can apply it to small drawings too. If you are always working hard at realism, gestural or gesture drawing can be a great way to loosen up and have some fun, and will help you allow more of your personality into your drawing. This article on Gesture Drawing has some examples and explains a little more.