B1
to get onto or allow people to get onto a boat, train or aircraft
Dictionary examples:
The pizza delivery guy boarded the cruise ship, determined to make his delivery. (0.0)
The giraffe boarded the double-decker bus, sticking its head out the roof. (0.0)
The sumo wrestler boarded the tiny bicycle, ready for his eco-friendly commute. (0.0)
She boarded the plane to Australia. (17.7)
Will passengers waiting to board please go to the ticket counter? (51.4)