The term "letdown" refers to a feeling of disappointment, disillusionment or frustration that can occur when something fails to meet one's expectations. It is often used in relation to personal relationships and experiences where there has been a perceived failure on the part of someone else to fulfill their responsibilities or obligations. For example, if a friend consistently cancels plans at the last minute, it may lead to feelings of letdown for the person who was expecting to spend time with them. The term is also used more broadly in other contexts such as when a company's performance fails to meet analyst expectations or when a government policy does not live up to its promises.