From over- + skirt.
overskirt (plural overskirts)
- A skirt worn visibly, especially over another layer, such as a petticoat.
2009 July 19, Anita Gates, “Goofy Fun, With Dapper Men”, in New York Times[1]:Agnès’s dress is very attractive too, but the overskirt did remind me of some old Ralph Lauren sheets I used to have.