Which word signifies a significant and often sudden decrease in quantity?

The word "deplete" signifies a significant and often sudden decrease in quantity. It comes from the root "plete," which means to fill, and the prefix "de-" implies removal or reduction. Thus, when something is depleted, it means that it has been significantly reduced or emptied, often in a rapid manner. This term is commonly used in various contexts, such as the depletion of resources, where there is a large consumption leading to a notable shortage.

In contrast, other options do not align with the notion of a sudden decrease. "Deposit" refers to putting something down or placing it, which does not indicate a reduction. "Defiance" denotes open resistance or bold disobedience and is unrelated to quantity changes. "Debacle" refers to a sudden and disastrous collapse or failure but does not specifically mean a decrease in quantity.