To instantaneously obliterate an object, usually in a video game.
Go for the sniper on the... BOOMDOWN, nice shot Jack
Similar to "sundowning" (Def.: 'a neurological phenomenon associated with increased confusion and restlessness in people with delirium or some form of dementia') though instead of a potential dementia or delirium diagnosis, the person is fully cognizant of their behavior and opinions with full agency.
"Rudy Giuliani is claiming that he was criminally assaulted in a grocery store, but everyone concluded that he was actually just boomdowning."