bullhead
n
1 any of various small northern mainly marine scorpaenoid fishes of the family Cottidae that have a large head covered with bony plates and spines
2 any freshwater North American catfish of the genus Ameiurus (or Ictalurus), having a large head bearing several long barbels
3 a scorpion fish, Scorpaena guttata, of North American Pacific coastal waters
4 Informal a stupidly stubborn or unintelligent person
bullhead rail
n (Railways) a rail having a cross section with a bulbous top and bottom, the top being larger
Now largely superseded by →
flat-bottomed rail