'let down' definitions:

Definition of 'let down'

From: WordNet
verb
Move something or somebody to a lower position; "take down the vase from the shelf" [syn: lower, take down, let down, get down, bring down] [ant: bring up, elevate, get up, lift, raise]
verb
Fail to meet the hopes or expectations of; "Her boyfriend let her down when he did not propose marriage" [syn: disappoint, let down]

Synonyms of 'let down'

From: Moby Thesaurus