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1.
Sempai is a Japanese honorific made popular in English dubs. It means 'mentor' or 'senior', depending on the context.

Not to be confused with the Malaysian street slang 'sempoi' or my friend Kambink_Sempoy.
"Ash introduced me to the blogging world, my blogger sempai" -Nadya
by Ash of Rilated April 11, 2005