1) Black-tie 2) Chic 3) Elegant, like a frock 4) Fancily decked out 5) Fancy 6) Fancy in apparel 7) For formal affairs 8) For formal occasions 9) For formals 10) Formal 11) Formal, fashion-wise 12) Formal, fashionwise 13) Formal, for wear 14) Formal, sartorially 15) Formally attired 16) In fancy clothing 1) Chic 2) Fancy 
• (a.) Showy in dress; attentive to dress.
Dress'y adjective Showy in dress; attentive to dress. « A dressy flaunting maidservant.» T. Hook. « A neat, dressy gentleman in black.» W. Irving. 
[adj] - (informal) in fancy clothing
adjective in fancy clothing
appropriate to somewhat formal occasions: an outfit that's a little too dressy for office wear. · showy in dress; stylish: a rather dressy reception.