1. On board a ship, train, aircraft, or other passenger vehicle.
2. At the side; alongside.
3. In or into a group, organization, or business: brought aboard two new designers.
4. Baseball On base.
On board of; on; in.
[Middle English abord : a-, on; see A-2 + bord, ship (from Old English bord).]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.