The Collaborative International Dictionary of English v.0.48:
Upside down \Up"side down`\, adv. in such a manner that the part normally pointed upward is pointed downward; same as upsidown and upsodown. [PJC]The Collaborative International Dictionary of English v.0.48:
Upsidown \Up"si*down`\, adv. See Upsodown. [Obs. or Colloq.] --Spenser. [1913 Webster]