an accepted way of dressing for a particular occasion or in a particular social group

Most evenings there's a party and the dress code is strict - black tie only. 晚上大多都有聚会，而且着装要求很严格——必须穿晚礼服。

a set of rules for what you can wear

My school had a very strict dress code. 我校的着装规定非常严格。