plague, plagued, plaguing 1. Any contagious, malignant, epidemic disease that causes high mortality; a pestilence. 2. An acute disease of rodents due to a bacterium, Yersinia pestis, transmitted to humans through the bite of infected fleas, or by inhalation. 3. The human disease is usually divided into three clinical forms: bubonic, septicemic, a... Found on http://www.wordinfo.info/words/index/info/view_unit/3360/