Jackpost
A person who acts like they're the king of the world but is actually a total piece of garbage.
My cousin is a jackpost. He bragged about his video game stats for 2 hours and then cried when he lost.
My boss is a jackpost. He yells at everyone but can't even fix his own coffee.
My friend's ex is a jackpost. She texted me 10 times in 5 minutes just to say she was 'feeling lonely.'