acanthopterygian (?æk?n???pt??r?d???n) adj (Zoology) of, relating to, or belonging to the Acanthopterygii, a large group of teleost fishes having spiny fin rays. The group includes most saltwater bony fishesn (Animals) any fish belonging to the Acanthopterygii[C19: from New Latin Acanthopterygii, from acantho- + Greek pterúgion fin]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ac?an?thop?ter?yg?i?an (?æk ?n???p t??r?d? i ?n) adj. 1. belonging or pertaining to the Acanthopterygii, the group of spiny-finned fishes, including the bass and perch. n. 2. an acanthopterygian fish. [1825?35;