anseriform adjective 1noun 1forms 3 adjective1 •Of or pertaining to birds of the order Anseriformes including ducks, geese, swans, and screamers.For more than a century anseriform birds were considered to have been closely related to, and to have originated from, the game fowl of the order Galliformes. — 2004 noun1 •Any bird of the order Anseriformes formsanseriforms · more anseriform · most anseriform