Entry 2 senses Webster, 1913 Parasitism /(păr"ȧ*sī`tĭz'm; 277)/ · Par·a·si·tism · IPA /ˈpæɹəs(a)ɪˌtɪzm̩/ 01 n. The state or behavior of a parasite; the act of a parasite. 1. The state or behavior of a parasite; the act of a parasite. 2. The state of being parasitic.(Bot. & Zool.)