† fanˈtasticoObs. [It.; corresp. to fantastic.] An absurd and irrational person. 1597Shakes.Rom. & Jul. ii. iv. 30 (Qo. 1) Limping antique affecting fantasticoes [fol. 1623 ed. phantacies] these new tuners of accents.1600Dekker FortunatusWks. 1873 I. 117, I have..seene fantasticoes.