from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Carried or used aboard a vehicle or vessel: onboard radar systems.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Carried or used on or in a vehicle or vessel
- adv. On or in a vehicle or vessel; aboard; on board.
From on board, equivalent to on- + board. (Wiktionary)