The qualification sporadic, indicating that occurrences of some phenomenon are rare and not systematic, can be used for:
Mathematics Sporadic group, any of a small number of finite groups that do not fit into any infinite family of groups
Medicine Sporadic disease, one with no recognisable pattern
Science Sporadic E propagation, an unusual form of radio propagation occasionally allowing long-distance communication Sporadic meteor, not part of a meteor swarm Sporadic permafrost, discontinuous permafrost that covers only a fraction of an area