The Collaborative International Dictionary of English v.0.48:

Embank \Em*bank"\, v. t. [imp. & p. p. Embanked; p. pr. & vb.
   n. Embanking.] [Pref. em- + bank. Cf. Imbank.]
   To throw up a bank so as to confine or to defend; to protect
   by a bank of earth or stone.
   [1913 Webster]