The definition of ditch someone is:
(verb) to break plans with someone without telling them
A: Is Willy coming to the party tonight?
A: I hate him so much! Do you want to ditch him?
B: Sure! Let’s leave him at the library!
Tammy is mad at her boyfriend because he was always ditching her to meet his friends.
I was supposed to meet my friends to see Dark Knight last night, but they ditched me! I’m so mad!