If you take enough of a drug that it makes you throw up, you did overdose. 'Overdose' doesn't mean you died. Fatal overdoses just get talked about more than other overdoses because they're the most harmful kind of overdose.
Alcohol abuse either kills people in the long term, or combined with automobiles. Very few people have a bit too much to drink some night and actually die from it. You'll generally black out long before you get a lethal dose.
With opioids, you can trivially take a lethal dose.
(That doesn't change what the word 'overdose' means. If you want to be more specific than the word is, feel free to use adjectives, e.g., 'fatal overdose', 'deadly overdose', etc.)
OD refers to excessive consumption or negative heath outcomes, so yes and sort of. With alcohol people will sometimes throw up before all that much alcohol enters the bloodstream, throwing up may qualify on its own but may prevent things like liver damage but throwing up itself could qualify as a negative health impact.
So for a collage kid throwing up really does provide meaningful protection for their liver. Though obviously it comes with its own risks of asphyxiation etc.