Aboard

1. On board of; onto or into a ship, boat, train, plane. [First attested around 1350 to 1470.]^[1]
2. Onto a horse. [First attested in the mid 20^th century.]^[1]
3. (obsolete) Across; athwart; alongside. [Attested from the early 16^th century until the late 17^th century.]^[1]