The Collaborative International Dictionary of English v.0.48:

Aboard \A*board"\, adv. [Pref. a- on, in + board.]
   1. On board; into or within a ship or boat; hence, into or
      within a railway car.
      [1913 Webster]

   2. Alongside; as, close aboard.
      [1913 Webster] (Naut.):

   To fall aboard of, to strike a ship's side; to fall foul
      of.

   To haul the tacks aboard, to set the courses.

   To keep the land aboard, to hug the shore.

   To lay (a ship) aboard, to place one's own ship close
      alongside of (a ship) for fighting.
      [1913 Webster]