least bittern(n = noun.animal) ixobrychus exilis - small American bittern;
is a kind of bittern
is a member of genus ixobrychus, ixobrychus

american bittern, at least, at the least, bittern, european bittern, in the least, last but not least, last not least, least, least common multiple, least effort, least of all, least resistance, least sandpiper, least shrew, least squares, line of least resistance, method of least squares, new world least weasel, old world least weasel, path of least resistance, the least bit