From Halopedia, the Halo wiki
Rejection is a Halo: Reach multiplayer medal depicted as a gold diamond superimposed by a blue shield and brass padlock. It's earned by using armor lock and surviving a subsequent assault that would have otherwise been fatal, i.e., a plasma mortar launched from a Zurdo-pattern Wraith. It was revealed alongside two other medals in Bungie's 07/09/10 weekly update. This medal is referred to as Denied in Halo: The Master Chief Collection as the Halo 4 Rejection medal was already in the game by the time Halo: Reach added to the collection.
- Ironically enough, if Armor Lock is used to destroy a vehicle, you are not awarded a rejection medal. Which is strange considering the only way to destroy a vehicle using Armor Lock is to have a vehicle, going fast enough to splatter you, hit you head on. Meaning, if you did not armor lock, you would have surely died, and therefore, should properly award you the medal.
- One theory could be that the splatter was coded in, rather than handled by physics or damage, so it sort of works outside the usual damage, which Bungie didn't realize.
- Oddly, one can earn this medal in Forge by setting the Damage Resistance to Invulnerable, walking into a Kill Ball, and activating armor lock.
- The medal can be obtained by using armor lock to block the EMP from another player's armor lock.