Which word should be used for the shape of a dress?

The word for the shape of the dress should be style.

style Basic vocabulary

English [sta?l] American [sta?l]

n. style; style; pattern; fashion; type.

The style of this skirt is just in season.

The style of this skirt is just in season.

Her clothes are always in style.

We have vases in various styles.

Usage:

Style as a noun means "style", which is transformed into a verb meaning "design". It can also mean "to call, name", i.e. to give someone or something a name.

Style is mostly used as a transitive verb, followed by a noun or pronoun as the object, but also a compound object with a noun as the complement. It can be used in passive constructions.