The correct spelling of the word "most puissa" is actually "most puissant". It is pronounced /moʊst ˈpwiːsənt/ in IPA phonetic transcription. The word "puissant" means powerful or mighty, and comes from the Old French word "puissant" which means the same thing. The addition of the suffix "-ant" to the Old French word "pui" creates the adjective form "puissant". So next time you encounter the word "most puissant", remember to spell it correctly!