What does this sentence mean? Why is she using "sick" here?
Native speaker’s answer
Rebecca
The word "sick" can have various informal and formal meanings. Here it is being used to describe something that is unpleasant. If you find something gross, creepy, gruesome or disgusting then it's sick. Rachel is saying that it is "sick" or "gross/weird" that Monica wants to have a relationship with a man who's father she has previously dated. Ex: I can't believe you ate the mystery meat. That's sick. Ex: I think it's a little sick to have a crush on your stepsister.