Disappointing describes something that lets you down or doesn't meet your expectations. A disappointing movie doesn't live up to its exciting trailer. A disappointing grade reflects work that didn't reach the standard you hoped for. When half the rides at the amusement park are closed for repairs, or when the sandwich that looked amazing in the menu photo arrives small and soggy, those experiences are disappointing.

Something becomes disappointing when reality falls short of what you hoped for. The bigger the gap between what you expected and what actually happened, the more disappointing it feels. Some disappointing things are minor, like rain on a beach day. Others feel more serious, like a canceled birthday party or not making the team you tried out for.