1.  bullhead(n = noun.animal) - freshwater sculpin with a large flattened bony-plated head with hornlike spines;
is a kind of sculpin
is a member of cottus, genus cottus

2.  bullhead(n = noun.animal) bullhead catfish - any of several common freshwater catfishes of the United States;
is a kind of catfish, siluriform fish
is a member of ameiurus, genus ameiurus
has particulars: ameiurus melas, horned pout, hornpout, pout, brown bullhead

1.  A fresh-water fish of many species, of the genus Uranidea, esp. Uranidea gobio of Europe, and Uranidea Richardsoni of the United States; -- called also miller's thumb. [1913 Webster]

2.  The black-bellied plover (Squatarola helvetica); -- called also beetlehead. [1913 Webster]

3.  A stupid fellow; a lubber. Jonson. [1913 Webster]

4.  A small black water insect. E. Phillips. [1913 Webster]

bullhead, n. any of various marine fishes with large flattened heads.

armed bullhead, brown bullhead