A coronation gown is a gown worn by a royal lady becoming a queen at her coronation. The design may vary, but it generally has covered shoulders. A royal robe is generally worn over it. The crown, sceptre and orb complete the attire. Coronation gowns are also worn by queen consorts, although theirs is generally more simple than the elaborate versions worn by queen regnants.
References
Coronation gown Wikipedia(Text) CC BY-SA