merdus Save DMLBS merdus [cf. merda, mergus] , kind of aquatic bird (iron., with play on merda and mergus, as on ‘foul’ and fowl’ ). pervagabant totam insulam Anglicanam ~i sive mergi hujusmodi, insidiantes egrotantibus Ad. Eyns. Hug. V 17 p. 204.