adverb
overboard
OH-ver-bord/ˈoʊvərˌbɔrd/
Over the side of a boat into the water.
The sailor falls overboard while a companion reaches down to help.

Etymology
With bord meaning a ship's side, the compound literally describes going over that side. The boundary crossed is the edge of the vessel, giving the sense of leaving the boat and entering the water.
In context
Discards are these fish they weren't targeting and they get thrown overboard wastefully.
And the book is lined in lead, so that if the ship is attacked, it can be thrown overboard.
More examples
- The sailor jumps overboard to rescue the dog.
- A wave washes our fishing gear overboard.
- Please don't throw trash overboard.