On board; into or within a ship or boat; hence, into or within a railway car. / On or onto a horse, a camel, etc. / (baseball) On base. / Into a team, group, or company. / (nautical) Alongside.

On board of; onto or into a ship, boat, train, plane. / Onto a horse. / (obsolete) Across; athwart; alongside.

A cry to passengers to board a train or boat that is soon to depart.

(nautical) To strike (the side of another ship).