תַּנִּין This word was sometimes translated as Dragon, Serpent or Whale. Dragon seems to be the correct fit and gives some consistency between New and Old Testament Idioms. The only place where this doesn’t fit as well as expected is in Exodus chapter 7 where Aaron cast down the staff and it became a ??? Serpent seems to fit better but that is another Hebrew word. So in my translation he cast down the staff and it becomes a Dragon. Where Moses cast down the staff at the burning bush it becomes a serpent which is a different word. So if you take serpent to be a subset of dragon this all works. It might seem better to use reptile instead of dragon but Dragon is clearly in the New Testament in the Greek. I’m pretty confident the Greek word for Dragon matches this word in the Hebrew, we just might need to give some thought as to what we consider to be a dragon.