From AMS Glossary
A stable equilibrium state having the property that small departures from the equilibrium continually diminish.
An attractor may be represented in a coordinate system as a single point (the usual case) or as a bounded set of infinitely many points (as in the case of a limit cycle). A strange attractor is an attractor containing an infinite number of points and having the property that small changes in neighboring states give rise to large and apparently unpredictable changes in the evolution of the system. The best-known example of a strange attractor in meteorology is that discovered by E. N. Lorenz (1963) in solutions to a simplified set of equations describing the motion of air in a horizontal layer heated from below.
Lorenz, E. N. 1963. Deterministic nonperiodic flow. J. Atmos. Sci.. 20. 130–141.