Definition of "spearfish"

Any of the genus Tetrapturus of marlins, a type of fish with the upper jaw elongated into a spearlike bill.  examples

Any striped marlin (Kajikia audax)  examples

Any quillback (Carpioides cyprinus  examples

To try to catch a fish using a spear or spear gun.  examples

To fish for spearfish by any method.  examples