Sporadic group
Finite simple group type not classified as Lie, cyclic or alternating
In the mathematical classification of finite simple groups, there are a number of groups which do not fit into any infinite family. These are called the sporadic simple groups, or the sporadic finite groups, or just the sporadic groups. A simple group is a group G that does not have any normal subgroups except for the trivial group and G itself.
From Wikipedia, under CC BY-SA. More on occurri.