Aboard

on board; on, in, or into a ship, train, airplane, bus, etc.:
to step aboard.
alongside; to the side.
baseball. on base:
a homer with two aboard.
into a group as a new member:
the office manager welcomed him aboard.
on board of; on, in, or into:
to come aboard a ship.
all aboard!, (as a warning to p-ssengers entering or planning to enter a train, bus, boat, etc., just before starting) everyone get on!
contemporary examples

then out of the mist, a whirring of helicopter blades, and, deus ex machina, a man descends fromt he chopper to winch you aboard.
girl rescued by prince william speaks! tom sykes august 29, 2012

napoleon solved the matter by ordering his officers to stuff her into a litter and carry her aboard by force.
pauline bonaparte: dead cool simon doonan november 29, 2009

aboard the qantas a380, the computers were overwhelmed by a firestorm of error messages and basically gave up.
2010’s unsafe skies clive irving december 29, 2010

a snapshot of presidential candidate gary hart aboard the yacht “monkey business” ended his aspirations forever.
don’t ask, don’t tell turncoats linda hirshman november 30, 2010

the three roadies—joe dan, kim, and red dog—and the sound technician, michael callahan—all aboard.
stacks: hitting the note with the allman brothers band grover lewis march 14, 2014

historical examples

they are here, aboard the frigate which brought me, your highness.
a romance of the west indies eugne sue

if you haven’t time to hear it now, i will tell you aboard ship.
brave and bold horatio alger

we don’t know what’s aboard it, and we don’t know where it came from, but it’s our prize.
derelict alan edward nourse

very well, then, be ready, men; we’ll be aboard ’em in a minute or two.
howard pyle’s book of pirates howard pyle

half an hour later he was aboard of the cars, little dreaming of the surprise in store for him.
from farm to fortune horatio alger jr.

adverb, adjective, preposition (postpositive)
on, in, onto, or into (a ship, train, aircraft, etc)
(nautical) alongside (a vessel)
all aboard!, a warning to p-ssengers to board a vehicle, ship, etc
adv.

late 14c., probably in most cases from old french à bord, from à “on” + bord “board,” from frankish -bord or a similar germanic source (see board (n.2)); the “boarding” or sides of a vessel extended to the ship itself. the usual middle english expression was within shippes borde. the call all aboard! as a warning to p-ssengers is attested from 1838.