Sitting meditation as practiced in the Zen School of Buddhism. In Zen Buddhism, zazen (literally "seated meditation") is a meditative discipline that is typically the primary religious practice. The precise meaning and method of zazen varies from school to school, but in general it can be regarded as a means of insight into the nature of existence. In the Japanese Rinzai school, zazen is usually associated with the study of koans. The Sōtō School of Japan, on the other hand, only rarely incorporates koans into zazen, preferring an approach where the mind has no object at all, known as shikantaza.
Example via www.ramdass.org: Meditation and Expectations