definition decline
1 An example of decline is the collapse of the Roman Empire. 2  An example of decline is the quality of a glass of milk as it starts to sour over time. 3  An example of decline is the failing health of someone with cancer.  Decline is defined as to refuse something, slope downward, become less or to sink from view. 1  An example of decline is someone saying no when they've been asked out to dinner.  An example of decline is a ski run.