Boa \Bo"a\ (b[=o]"[.a]), n.; pl. {Boas}. [L. boa a kind of water serpent. Perh. fr. bos an ox.] 1. (Zool.) A genus of large American serpents, including the boa constrictor, the emperor boa of Mexico ({Boa imperator}), and the chevalier boa of Peru ({Boa eques}). [1913 Webster] Note: The name is also applied to related genera; as, the {dog-headed boa} ({Xiphosoma caninum}). [1913 Webster] 2. A long, round fur tippet; -- so called from its resemblance in shape to the boa constrictor. [1913 Webster]