Source : Webster's Revised Unabridged Dictionary (1913)

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

   2. Alongside; as, close aboard. 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.

Aboard \A*board"\, prep.
   1. On board of; as, to go aboard a ship.

   2. Across; athwart. [Obs.]

            Nor iron bands aboard The Pontic Sea by their huge
            navy cast.                            --Spenser.

Source : WordNet®

aboard
     adv 1: on a ship, train, plane or other vehicle [syn: {onboard}]
     2: on first or second or third base; "Their second homer with
        Bob Allison aboard" [syn: {on base}]
     3: side by side; "anchored close aboard another ship" [syn: {alongside}]
     4: part of a group; "Bill's been aboard for three years now"