Entry 1 sense Webster, 1913 Fantastically /făn-tăs'-tĭk-lē/ · Fan·tas·tic·al·ly · IPA /fæntˈæstɪkliː/ 01 adv. In a fantastic manner. 1. In a fantastic manner. “the letter A, in scarlet, fantastically embroidered with gold thread, upon her bosom.” — Hawthorne.