The Collaborative International Dictionary of English v.0.48:

Holcad \Hol"cad\, n. [Gr. 'olka`s, -a`dos, a ship which is
   towed, a ship of burden, fr. 'e`lkein to draw. Gf. Hulk.]
   A large ship of burden, in ancient Greece. --Mitford.
   [1913 Webster]