/euh bawrd", euh bohrd"/ , adv.
1. on board; on, in, or into a ship, train, airplane, bus, etc.: to step aboard.
2. alongside; to the side.
3. Baseball. on base: a homer with two aboard.
4. all aboard! (as a warning to passengers entering or planning to enter a train, bus, boat, etc., just before starting) Everyone get on!
5. into a group as a new member: The office manager welcomed him aboard.
prep.
6. on board of; on, in, or into: to come aboard a ship.
[ 1350-1400; ME abord ( e ) (see A- 1 , BOARD), perh. conflated with MF a bord ]