I. a‧board1 /əˈbɔːd $ əˈbɔːrd/
preposition on or onto a ship, plane, or train:
They finally went aboard the plane. [TahlilGaran] Dictionary of Contemporary English ▲
II. aboard2 adverb1. 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
[TahlilGaran] Dictionary of Contemporary English ▲