Oxford Dictionary English let-down noun noun BrE BrE//ˈlet daʊn// ; NAmE NAmE//ˈlet daʊn// [countable, usually singular, uncountable] (informal) Add to my wordlistjump to other resultssomething that is disappointing because it is not as good as you expected it to be synonym disappointment, anticlimax Afterwards there was just a feeling of let-down. The London exhibition was a bit of a let-down.Check pronunciation: let-down oxfordlearnersdictionaries.com