There are several synonyms for the phrase "dress clothes" that may come in handy when you are trying to describe attire for a fancier occasion. "Formalwear" is a popular term that refers to clothing suitable for a formal event, such as a fancy dinner or wedding. "Eveningwear" can be used to describe clothing that is appropriate for a nighttime event, such as a gala or charity ball. "Cocktail attire" or "cocktail dress" is a term used to describe clothing that is dressy but not overly formal, often appropriate for a semi-formal event or a fancy night out on the town. "Black-tie attire" is a formal dress code that usually requires a tuxedo or evening gown.