A drum circle is any group of people playing (usually) hand-drums and percussion in a circle. More recently, however, the term has also been used to designate a particular form of drum circle: a facilitated drum circle. For other kinds of drums, see drum (disambiguation). ... Percussion instruments are played by being struck, shaken, rubbed or scraped. ... In Euclidean geometry, a circle is the set of all points in a plane at a fixed distance, called the radius, from a fixed point, called the centre. ...
In this newer definition, a drum circle is a facilitated jam. Drums and/or percussion are handed out or already in place, and people come not to 'learn to drum' but simply to have fun playing together. The facilitator guides and encourages the participants to create exciting in-the-moment music. The term jam band is commonly used to describe psychedelic rock-influenced bands whose concerts largely consist of bands reinterpreting their songs as springboards into extended improvisational pieces of music. ...
Outwardly, a drumcircle is a group of people sitting or standing in a circle playing drums and percussion instruments together; from there, it can be anything the participants wish.
Most of the circles I have played in were in a middle ground: some improv, some specific rhythms, and led in a manner promoted by Arthur Hull, which he calls drumcircle facilitation.
A community drumcircle in the United States is a noisy and fun, family friendly event, where people come together in order share their spirit by entraining rhythmically as a percussion ensemble.