a·board 
(ə-bôrd)
(ə-bôrd)adv.
1. On board a ship, train, aircraft, or other passenger vehicle.
2. At the side; alongside.
3. In or into a group, organization, or business: brought aboard two new designers.
4. Baseball On base.
prep.
On board of; on; in.
[Middle English abord : a-, on; see A-2 + bord, ship (from Old English bord).]