The Collaborative International Dictionary of English v.0.48:

magnetic moment \magnetic moment\ n.
   The torque exerted on a magnet or dipole when it is placed in
   a magnetic field.

   Syn: moment of a magnet.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

magnetic moment
    n 1: the torque exerted on a magnet or dipole when it is placed
         in a magnetic field [syn: magnetic moment, moment of a
         magnet]