In abstract algebra, a magma (or groupoid) is a basic kind of algebraic structure. Specifically, a magma consists of a set M equipped with a single binary operation M × M → M. A binary operation is closed by definition, but no other axioms are imposed on the operation.
The term magma for this kind of structure was introduced by Bourbaki. The term groupoid is an older, but still commonly used alternative which was introduced by Øystein Ore. However, groupoid also refers to an entirely different algebraic structure described at groupoid.
Reference:
http://en.wikipedia.org/wiki/Magma_%28algebra%29
