any wasting disease, as tuberculosis of the lungs
Webster’s New World College Dictionary, 4th Edition. Copyright © 2010 by
Houghton Mifflin Harcourt. All rights reserved.
Word origin of 'phthisis'L < Gr, a decay < phthiein, to waste away < IE base *gwhthei-, to disappear, be destroyed > Sans kṣáyati, (he) destroys