Thug: " Oh yeah, well I dorsal finned this guys scrotum so hard that his testes fell out."
Horniest person in your group
Completely brain dead individual
Sassy to the point of hilarity
To be honest this person is just so stupid that he/she thinks that dorsal fin could possibly be an insult. I mean seriously, dolphins are one of the smartest animals that we know of today. How could anything remotely involving a dolphin be an insult?
See also, Beer Gut, Dunlop Disease, or Spare Tire.