let (one's) hair down
To drop one's reserve or inhibitions

[TahlilGaran] Dictionary of Contemporary English ▲

let one's hair down
ENJOY ONESELF, have a good time, have fun, make merry, let oneself go, have a ball, whoop it up, paint the town red, live it up, have a whale of a time, let it all hang out

[TahlilGaran] Dictionary of Contemporary English ▲

let hair down
let (your) hair down
to relax and do what you want.
The party gives you a chance to let your hair down at the end of the week.

[TahlilGaran] English Idioms Dictionary ▲

let one's hair down
to act freely and naturally, to relax
We were able to let our hair down at the party and have a good time.

[TahlilGaran] English Idioms Dictionary ▲