ワンピース

noun

dress; one-piece dress

Refers to a woman's one-piece dress. Corresponds to English 'one-piece'.

from English one-piece

• 彼かの女じょは花はな柄がらのワンピースを着きていた。

  She was wearing a floral-patterned dress.

noun which may take the genitive case particle 'no'

one-piece (swimsuit, etc.)

Used attributively with の for one-piece items, most commonly swimsuits. Less common than sense 1.