1. Upon which.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• whereup,
• whereapon,
• wareupon,
• qhereupon,
• ahereupon,
• shereupon,
• ehereupon,
• 3hereupon,
• 2hereupon,
• wgereupon,
• wbereupon,
• wnereupon,
• wjereupon,
• wereupon,
• wherupon,
• whareupon,
• whoreeson,
• Wertunon,
• Wherenupup,
• Beareepon

The adjective form of the word "whereupon" is "whereupon".