It's mean to ruin someone's reputation.
Pat is a senior in high school and is about to graduate.
Pat wants to make a speech at the graduation.
Pat makes a speech at her graduation and it is a good speech.
Pat makes a speech at her graduation in her speech she ruins the reputation of a girl she has never liked in her school.
Everyone loves Pat's speech and give her a round of applause.
Pat is removed from the stage by the principal and everyone laughs at her.