A person, often a child, that becomes so overcome with all the attention that they lose their composure and become rude and selfish and behave poorly on their birthday.
Did you see your grandchild? She became such a birthday brat at her party. She was screaming and throwing a tantrum in front of everybody!
by amesababe December 18, 2010
A person that expects everyone to recognize and celebrate them without ceasing on their birthday. The day is often accompanied with emotional breakdowns.
Dudley Dursley whined and whined about his gifts on his birthday, something only a birthday brat would do.
by WhiteBoyPlayThatFunkyMusic April 25, 2017