If someone is monodramatic, they are always talking about the same thing or have only one way of acting or feeling.
Being monodramatic might make people feel bored or annoyed.
Examples:
She is so monodramatic, she only talks about her cat.
He's very monodramatic, he always acts the same way.
My friend is monodramatic, she only likes one kind of food.
My brother is so monodramatic, he only wears one color.
The robot is monodramatic, it only says one thing.
The movie is monodramatic, it only has one character.