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Webster 1913 Edition

adv.

Over the side of a ship; hence, from on board of a ship, into the water;

as, to fall

overboard

adv.

Literally, over the side of a ship; hence, out of a ship or from on board; as, to fall overboard; which of course is to fall into the water.

overboard ‎(not comparable)

overboard ‎(not comparable)

Over the edge; especially, off or outside of a boat.
It was their practice to throw the scraps overboard.‎
- 1913, Joseph C. Lincoln, chapter 8, in Mr. Pratt's Patients:
  Afore we got to the shanty Colonel Applegate stuck his head out of the door. His temper had been getting raggeder all the time, and the sousing he got when he fell overboard had just about ripped what was left of it to ravellings.
Excessively; too much.
They really went overboard with the party preparations.‎

over the edge, off a boat

Norwegian:

Bokmål: over bord

Nynorsk: over bord
Portuguese: borda a fora, exceder (pt)
Russian: за́ борт ‎(zá bort) (direction), за бо́ртом ‎(za bórtom), за борто́м ‎(za bortóm) (location)