[{"Bold_text": "noun", "List Items": ["any freshwater or marine coelenterate of the class Hydrozoa, including free-swimming or attached types, as the hydra, in which one developmental stage, either the polyp or medusa, is absent, and colonial types, as the Portuguese man-of-war, in which both medusa and polyp stages are present in a single colony."]}, {"Bold_text": "adjective", "List Items": ["belonging or pertaining to the Hydrozoa."]}]