let somebody/something ↔ down phrasal verb ( see also ↑ let )
1 . to not do something that someone trusts or expects you to do:
She had been let down badly in the past.
The worst feeling is having let our fans down.
let the side down British English (=disappoint a group of people that you belong to)
2 . to make someone or something less successful or effective:
McKenzie’s judgement rarely lets him down.
3 . to move something or someone to a lower position:
Let down a rope so that I can climb up.
Carefully, she let herself down into the water.
4 . let your hair down informal to relax and enjoy yourself, especially after working hard:
Visitors young and old let their hair down and enjoyed the show.
5 . let your guard/defences down to relax and stop worrying about what might happen or what someone might find out about you:
Maggie never really lets her guard down, does she?
6 . let somebody down lightly/gently to give someone bad news in a way that will not upset them too much:
I get asked out on dates quite often, but I always try to let the guy down gently.
7 . British English to allow the air to escape from something so that it loses its shape and becomes flat:
Someone’s let my tyres down!
8 . to make a piece of clothing longer by unfolding a folded edge OPP take up