The Collaborative International Dictionary of English v.0.48:
Black snake \Black" snake`\ (sn[=a]k) or Blacksnake \Black"snake\, n. (Zool.) A snake of a black color, of which two species are common in the United States, the Bascanium constrictor, or racer, sometimes six feet long, and the Scotophis Alleghaniensis, seven or eight feet long. [1913 Webster] Note: The name is also applied to various other black serpents, as Natrix atra of Jamaica. [1913 Webster]