• proppropro,
• propporpro,
• proprorpo,
• prorpopro,
• proporpro,
• proporopr

• prophesy,
• proxy,
• proponent,
• prove,
• profound,
• propane,
• prophetic,
• propose,
• proportional,
• properly,
• proportion.

The plural form of the word "propropro" is "propropros".

The singular form of the word "propropro" is "propropro". The word does not change in singular form because it doesn't exist as a recognized word in the English language.