isentropic

from WordNet (r) 3.0 (2006)

isentropic
    adj 1: with unchanging entropy; at constant entropy

from The Collaborative International Dictionary of English v.0.48

Isentropic \I`sen*trop"ic\, a. [Is- + entropy + -ic.] (Physics)
   Having equal entropy.
   [1913 Webster]

   {Isentropic lines}, lines which pass through points having
      equal entropy.
      [1913 Webster]