upside down

American  

adverb

1. with the upper part undermost.

2. in or into complete disorder; topsy-turvy.

   The burglars turned the house upside down.

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upside down British  

adjective

1. (usually postpositive; upside-down when prenominal) turned over completely; inverted

2. informal (upside-down when prenominal) confused; muddled; topsy-turvy

   an upside-down world

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adverb

1. in an inverted fashion

2. in a chaotic or crazy manner

Other Word Forms

Derived Forms

• upside-downness
  noun
• upside-down
  adjective

Etymology

Origin of upside down

1300–50; re-formation ( see upside) of Middle English upsedoun, earlier up so doun ( see up, so ¹, down ¹; sense of so obscure)

Example Sentences

And there can be little argument that PIF's £3.8bn investment over nearly five years turned the pro game upside down.

From BBC • Apr. 30, 2026

So far this year, the Iran war has turned OPEC’s usual production problem upside down.

From Barron's • Apr. 28, 2026

"The results are a surprise. They turn our understanding of the evolution of the eye and the brain upside down," says Dan-E Nilsson, professor emeritus in sensory biology at Lund University.

From Science Daily • Apr. 27, 2026

The plan was made public in January 2020, a few months before the pandemic turned the world upside down.

From The Wall Street Journal • Apr. 22, 2026

One time they even pulled it off hanging upside down from the ceiling.

From "Amari and the Night Brothers" by B.B. Alston