The Collaborative International Dictionary of English v.0.48:

Chank \Chank"\ (ch[a^][ng]k), n. [Skr. [,c]a[.n]kha. See
   Conch.] (Zool.)
   The East Indian name for the large spiral shell of several
   species of sea conch much used in making bangles, esp.
   Turbinella pyrum. Called also chank shell.
   [1913 Webster]