to make sb / sth less successful than they / it should be; to fail to help or support sb as they had hoped or expected
let sb / sth down
to make sb / sth less successful than they / it should be
She speaks French very fluently, but her pronunciation lets her down.
let sb down
to fail to help or support sb as they had hoped or expected
I'm afraid she let us down badly.
let sth down
to let or make sth go down
We let the bucket down by a rope.
let sth down
to make a dress, skirt, coat, etc. longer, by reducing the amount of material that is folded over at the bottom
let sth downbritánico
to allow the air to escape from sth deliberately
Some kids had let my tyres down.
Definiciones del Oxford Advanced Learner's Dictionary, 9.ª edición