large long-jawed oceanic sport fishes; related to sailfishes and spearfishes; not completely cold-blooded i.e. able to warm their brains and eyes
"The captain explained that the massive marlin they were chasing could actually regulate its brain temperature, making it a uniquely fierce opponent among large oceanic sport fishes."
Any species of game fish belonging to either of the genera Tetrapturus or Makaira. Every such species has a pointed, spear-like projection of the upper jaw.
"The captain adjusted his net carefully as he spotted a massive marlin leaping from the ocean with its distinctive bill piercing the air."
A surname.
"The Marlin family has lived in that coastal town for three generations."