What does it mean when a magnet is diamagnetic?

Diamagnetism is a type of magnetism that aligns itself perpendicular to the direction of an object's magnetic field and thus has a repulsive force. All materials are diamagnetic to some degree, but only when exposed to an externally applied magnetic field. The effect is generally weak in most materials and is completely overwhelmed in materials that have other magnetic properties. However, the effect of diamagnetism can be enhanced by introducing superconductors into the magnetic circuit.