to destroy or reduce the pleasure, interest, or beauty of something:
He tried not to let the bad news spoil his evening.
The oil spill has spoiled the whole beautiful coastline.
spoil something for someone I haven't seen the film, so don't spoil it for me by telling me what happens.
spoil your appetite You'll spoil your appetite for dinner if you have a cake now.
When food spoils or is spoiled, it is no longer good enough to eat:
The dessert will spoil if you don't keep it in the fridge.
to mark a ballot paper so that it cannot be officially counted as a vote:
Since she supported none of the candidates, she spoiled her ballot paper.