Pronunciation: ' ə p- ˌ s ī d- ' dau ̇ n
Function: adverb
Etymology: alteration of Middle English up so doun, from up + so + doun down
Date: 15th century
1 : in such a way that the upper and the lower parts are reversed in position
2 : in or into great disorder <turned their world upside down >
– upside-down adjective