a class of models in statistical physics. Spin glasses are disordered magnetic materials in which the orientation of nearby magnetic dipoles may be either parallel or antiparallel. This "preference" for one polarity or the other varies sinusoidally in space. Thus whether two dipoles prefer to orient in the same direction or in opposite directions and how much so depends on their precise distance apart. The configuration space of a spin-glass has an energy landscape which is directly analogous to a fitness landscape.
cf. field.