From Longman Dictionary of Contemporary Englishletdownlet‧down /ˈletdaʊn/ ●○○ noun [singular] informalDISAPPOINTED an event, performance etc that is not as good as you expected it to be SYN disappointment The end of the book was a real letdown. → let down at let1
Examples from the Corpus
letdown• Waldon has vowed not to let a letdown happen.• The general consensus is the show was a complete snooze, a letdown that garnered huge ratings and little else.• For the political right, Bolick said, the term just ended was a letdown when compared with last year.• The absence of it was a letdown.• The regents were a big letdown.• It will be a major letdown if we lose the game to Kansas.• Adding to a potential letdown, the triple was first waved off and then restored after the referees convened at midcourt.• The nation is mired in the muck of post-Superbowl letdown. 