The Collaborative International Dictionary of English v.0.48:

geophysics \geophysics\ n.
   A branch of geology that uses physical principles to study
   the properties of the earth.

   Syn: geophysical science.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

geophysics
    n 1: geology that uses physical principles to study properties
         of the earth [syn: geophysics, geophysical science]