upside down

UK: /ˌʌpsaɪdˈdaʊn/

WordReference Random House Learner's Dictionary of American English © 2026

ˈup•side ˈdown, adv. 

1. with the upper part at the bottom.
2. in or into complete disorder;
   topsy-turvy:
   turned the room upside down in their search.

WordReference Random House Unabridged Dictionary of American English © 2026

up′side down′, 

1. with the upper part undermost.
2. in or into complete disorder;
   topsy-turvy:
   The burglars turned the house upside down.
• 1300–50; re-formation (see upside) of Middle English upsedoun, earlier up so doun (see up, so¹, down¹; sense of so obscure)
up′side-down′, adj. 
up′side-down′ness, n. 

Collins Concise English Dictionary © HarperCollins Publishers::

upside down adjective

1. (usually postpositive; upside-down when prenominal) turned over completely; inverted
2. (upside-down when prenominal) confused; muddled; topsy-turvy: an upside-down world

adverb

1. in an inverted fashion
2. in a chaotic or crazy manner

Etymology: 16th Century: variant, by folk etymology, of earlier upsodown