I. a ‧ board 1 /əˈbɔːd $ əˈbɔːrd/ BrE AmE preposition
on or onto a ship, plane, or train:
They finally went aboard the plane.
II. aboard 2 BrE AmE adverb
1 . on or onto a ship, plane, or train:
The plane crashed, killing all 200 people aboard.
The boat swayed as he stepped aboard.
2 . All aboard! spoken used to tell passengers of a ship, bus, or train that they must get on because it will leave soon