(suffix) courtesy title, used after the surname or name of a senior person, at work or school.
Used when referring to another student, club member, etc, who is your senior.
Senior, elder, predecessor
Senior, elder, or upperclassmen. Used in cases where the subject is a superior within the same social class.
(also: sempai): upperclassman (ie. Kuno-senpai)
a social elder. The term is usually used in work or at school; the senpai is opposite to kouhai. Mamoru is Asanuma's senpai, because Mamoru is a more senior student at their school.
Suffix used towards an elder/senior/older student.
An honorific used by a young person when talking to or about a benefactor or senior in a social organization. The usage of this honorific is encountered time and again in anime, mostly when students are talking to or about their senior classmates, as in "Tamiya-sempai heads the campus motorcycle club." Used as a noun, it would just mean, "our seniors", or "our upperclassmen".
Japanese term (sometimes an honorific) for a person in a club or other organization, including a school or college, who is a senior (in other words, a member for longer or of a higher year) and mutually recognized as such. The junior counterpart is called . Senpai is often seen romanized as sempai, in accordance with the initial version of the Hepburn romanization system.