i Register
In some senses, aboard is marked as obsolete. Watch for register when choosing this word.
adv
On board; into or within a ship or boat; hence, into or within a railway car.
We all climbed aboard.
As the 1857 to Manchester Piccadilly rolls in, I scan the windows and realise there are plenty of spare seats, so I hop aboard. The train is a '221'+'220' combo to allow for social distancing - a luxury on an XC train as normally you're playing sardines, so I make the most of it.
On or onto a horse, a camel, etc.
to sling a saddle aboard
On base.
He doubled with two men aboard, scoring them both.
Into a team, group, or company.
The office manager welcomed him aboard.
Alongside.
The ships came close aboard to pass messages.
The captain laid his ship aboard the enemy's ship.
prep
On board of; onto or into a ship, boat, train, plane.
We all went aboard the ship.
Conditions were horrendous aboard most British naval vessels at the time. Scurvy and other diseases ran rampant, killing more seamen each year than all other causes combined, including combat.
Onto a horse.
Across; athwart; alongside.
Nor iron bands aboard The Pontic Sea by their huge navy cast.