• IPA: /ˌʌpsaɪd ˈdaʊn/, /ˌʌpsaɪˈdaʊn/

upside down (not comparable)

1. Inverted, so that the top is now at the bottom.

   The Union flag was flying upside down, a sign of danger.

2. In great disorder.

   The thief had turned the room upside down.

   • c. 1597, William Shakespeare, “The First Part of Henry the Fourth, […]”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies (First Folio), London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, OCLC 606515358 ↗, [Act I, scene i]:

     This house is turned upside down since Robin Ostler died.

• (inverted) bottom-upwards, topsy-turvy

• French: à l'envers, sens dessus dessous
• German: auf dem Kopf, verkehrt herum, verkehrt rum, umgekehrt
• Italian: a rovescio, sottosopra, al rovescio, a testa in giù, al contrario
• Portuguese: de cabeça para baixo, de ponta-cabeça
• Russian: вверх дно́м
• Spanish: al revés, boca abajo, bocabajo

• French: sens dessus dessous
• Italian: sottosopra, a soqquadro
• Portuguese: de pernas para o ar
• Russian: кувырко́м
• Spanish: de cabeza

upside down (not comparable)

1. Inverted; turned so that the top is at the bottom.

   The pattern resembled an upside down letter W.

2. In great disorder.
   • 1901, Amelia Edith Huddleston Barr, The lion's whelp: a story of Cromwell's time (page 248)

     The wenches and the men have been on the streets all day, and the kitchen is upside down. You never saw the like.

3. (finance) Owing more money for something than it is worth; having negative equity.

   He's upside down on his mortgage.

• (having negative equity) underwater

• French: à l'envers
• Italian: invertito, inverso, capovolto, rovesciato, a testa in giù
• Portuguese: de cabeça para baixo, de ponta-cabeça
• Spanish: al revés