- with the upper part undermost.
- in or into complete disorder; topsy-turvy: The burglars turned the house upside down.
- (usually postpositive; upside-down when prenominal) turned over completely; inverted
- (upside-down when prenominal) informal confused; muddled; topsy-turvyan upside-down world
- in an inverted fashion
- in a chaotic or crazy manner
late 15c., earlier upsadoun (late 14c.), up so down (c.1300); the so perhaps meaning “as if.”