Real Dictionary

valedictorian
countable noun: A valedictorian is the student who has the highest marks in their class when they graduate from high school, college, or university, and who gives a speech at their graduation ceremony.

valedictorian in American English
in schools and colleges, the student, usually the one highest in scholastic rank in the graduating class, who delivers the valedictory
noun: a student, usually the one ranking highest academically in a school graduating class, who delivers the valedictory at the commencement exercises

valedictorian in British English
adjective: saying goodbye
noun: a person, usually the most outstanding graduate, who delivers a farewell speech at a graduation ceremony