From Longman Dictionary of Contemporary Englishlet your hair downlet your hair downinformalRELAXED to enjoy yourself and start to relax, especially after working very hard The party gave us all a chance to really let our hair down. → hair
Examples from the Corpus
let your hair down• Chat rooms on the Internet are a place we can let our hair down and say what we think.• In the second half Complicite let their hair down in their own inimitable way.• This was the day our friends let their hair down and spoke with amazing frankness.• Out in the pasture, the princess let her hair down.• You can really let your hair down and do what you want at the club.• I spotted Juanita really letting her hair down on the dance floor.• Among the many booksellers and publishers whom I spotted letting their hair down on the dance floor was independent publisher Christopher Hurst.• Man's got ta let his hair down.• We know when we can afford to let our hair down and when we can't.• He liked this: what his pub was all about, for people to let their hair down.• Playing softball is just a good way to let your hair down and have fun. 