A person who is not only Republican, but choses to be extremely ignorant and likes to push his or her political views on those around them, whether they want to hear it or not.
RDBs often are big fans of Sean Hannity and Rush Limbaugh, and they think Fox News really is fair and balanced. They swear Barack Obama was born in Kenya, and they hate all things Obama, including his use of a teleprompter. RDBs often use buzzwords and phrases such as "fascism," "socialism," "The Great Ronald Reagan," and "they tuk our joooobs." RDBs loathe liberals and often refer to Obama as Muslim and by his full name, Barack Hussein Obama, with an emphasis on Hussein.
"Rush Limbaugh is a crazy RDB."
"That RDB doesn't even really know what fascism is, but he keeps spouting off about it."