aboard aboard /əˈbɔːrd/

adverb

1. () On a ship, train, plane or other vehicle  ( on board , aboard )
   on a ship, train, plane or other vehicle
     The passengers eagerly climbed aboard the ship, ready for their ocean adventure.
   The passengers eagerly climbed aboard the ship, ready for their ocean adventure.
   
2. () (baseball) on first, second or third base  ( aboard )
   (baseball) on first, second or third base
    Their second homer with Bob Allison aboard
   Their second homer with Bob Allison aboard
   
3. Part of a group  ( aboard )
   part of a group
    Bill's been aboard for three years now
   Bill's been aboard for three years now
   
4. Side by side  ( aboard , alongside )
   side by side
    Anchored close aboard another ship
   anchored close aboard another ship
   

preposition

1. () On or onto a ship, aircraft, train, or other vehicle.  ( aboard )
   On or onto a ship, aircraft, train, or other vehicle.