onesie

American  

[wuhn-zee] / ˈwʌn zi /

noun

1. a one-piece leisure or sleeping garment for an adult, usually combining a long-sleeved top with long pants.

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Trademark.

1. Onesies, a brand name for one-piece garments for infants, the lower portion resembling briefs and having snaps across the crotch for convenience in diapering. Although a trademarked term, it is often spelled as lowercase onesie, referring to a single garment.

onesie British  

/ ˈwʌnzɪ /

noun

1. a one-piece garment combining a top with trousers, worn by adults as leisurewear

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Usage

What else does onesie mean? A onesie is a one-piece item of loungewear or sleepwear. Traditionally, onesies are worn by babies, but they exploded into adult novelty fashion in the 2010s. How is onesie pronounced?[wuhn-zee]

Etymology

Origin of onesie

First recorded in 1980–85; originally a trademark

Example Sentences

An omen among omens: Mid-dog-walk that day, I spot a onesie that reads “Milk Drunk” and shudder at the impulse to recruit our newborns into low-key bacchanalia.

From Slate • May 10, 2026

As a parent, you wouldn’t want your child to be stuck forever wearing a onesie and drinking from a sippy cup.

From The Wall Street Journal • Jan. 1, 2026

Though the photo cuts off the top half of the cardigan-clad baby’s face, presumably for privacy reasons, her name can be seen boldly emblazoned — in gold, of course — on her plain white onesie.

From Los Angeles Times • Apr. 28, 2025

She had managed to consume 24 socks, a scrunchie, two hair ties, a shoe insert, a onesie and multiple pieces of cloth.

From Los Angeles Times • Feb. 26, 2025

They’d met at Princeton as undergraduates, and Brian had pictures of himself as a baby in a Princeton onesie.

From "Little Fires Everywhere" by Celeste Ng