Meaning of “board” - Learner’s Dictionary

board

verb uk us /bɔːd/
GET ON A VEHICLE [ I, T ]

B1 to get on a bus, boat, aircraft, etc:

He boarded the train to London.
TRAIN/AIRCRAFT ETC [ I ]

If an aircraft, train, etc is boarding, passengers are getting onto it:

The plane is now boarding at gate 26.

(Definition of “board verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)