antiaircraft: artillery designed to shoot upward at airplanes
gun: a weapon that discharges a missile at high velocity (especially from a metal tube or barrel)
cycadopsida: palmlike gymnosperms: includes the surviving order Cycadales and several extinct orders; possibly not a natural group; in some systems considered a class (Cycadopsida) and in others a subdivision (Cycadophytina or Cycadophyta)