A drum circle is any group of people playing (usually) hand-drums and percussion in a circle. They are distinct from a drumming group or troupe in that the drum circle is an end in itself rather than preparation for a performance. They can range in size from a handful of players to circles with thousands of participants.
In 1991, during testimony before the United States Senate Special Committee on Aging, Grateful Dead drummer Mickey Hart stated:
The term "Drum Circle" originated in the United States during the late 1960s and early 1970s for any group of people, particularly counterculture groups, who gather (informally) to play music together. The terms "drum jam" or "jam session" could be substituted. Settings include beaches, parks, concert parking lots, festivals, and retreats. The determining criteria for a drum circle is that the music is improvised and co-created by the participants. Drum circles may or may not be open to the public, but the music is always a group expression, not constrained by genre, instrumentation, or directed by and one person or sub-group.