one-piece
US /ˈwʌn.piːs/
UK /ˈwʌn.piːs/

1.
a garment made in one piece, especially a swimsuit or a baby's garment
:
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She wore a stylish one-piece swimsuit to the beach.
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The baby looked adorable in his fuzzy one-piece.
1.
made in a single unit or piece
:
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The new desk has a one-piece top, making it very sturdy.
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The engineer designed a one-piece casing for the electronic device.