The Collaborative International Dictionary of English v.0.48:

Thermodynamics \Ther`mo*dy*nam"ics\, n.
   The science which treats of the mechanical action or
   relations of heat.
   [1913 Webster]

WordNet (r) 3.0 (2006):

thermodynamics
    n 1: the branch of physics concerned with the conversion of
         different forms of energy

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "thermodynamics":
   Newtonian physics, acoustics, aerodynamics, aerophysics,
   applied physics, astrophysics, barodynamics,
   basic conductor physics, biodynamics, biophysics, calorimetry,
   chemical physics, cryogenics, crystallography, cytophysics,
   dynamics, electron physics, electronics, electrophysics,
   fluid dynamics, geodynamics, geophysics, hydrodynamics, kinematics,
   kinesiology, kinetics, macrophysics, magnetohydrodynamics,
   mathematical physics, mechanics, medicophysics, microphysics,
   myodynamics, natural philosophy, natural science, nuclear physics,
   optics, philosophy, physic, physical chemistry, physical science,
   physicochemistry, physicomathematics, physics, psychophysics,
   pyrotechnic, pyrotechnics, pyrotechny, radiation physics,
   radionics, solar physics, solid-state physics, statics,
   stereophysics, theoretical physics, thermochemistry, thermotics,
   zoodynamics, zoophysics