psycho

A psycho is someone who has an unhealthy obsession with someone or something.

The word "psycho" often gets used in popular culture to describe someone who's obsessed, usually to the point of being a bit creepy. For example, you might hear someone say, "He's such a psycho about his sports team, he's always talking about it and can't stop thinking about their next game." Or maybe your friend will joke that they're dating a "psycho" because their partner is so intense about them. In both cases, the word isn't being used in a super serious way – it's just a casual way to describe someone who's really into something or someone.

(Note: Some people might use the term "psycho" more seriously to refer to someone with a mental health condition like psychosis or schizophrenia. But in informal usage, as mentioned above, it usually carries a more playful connotation.)