[Idiom] you're cheating on a vegetable

[az01]

Hi, i watched a movie that had that phrase, but i couldn't figure it out. Does anyone know?
Thank you so much :-D

 

[SoothingDave]

It's not an idiom. You will need to provide some context if you hope to have us decipher it.

 

[Raymott]

This is a line from the movie, While You Were Sleeping.
Sandra Bullock pretends to be the fiance of a comatose man, but she falls in love with the guy's brother. She tells her boss about her dilemma. He answers something, and she says:
Bullock: You're sick!
Boss: I'm sick? You're cheating on a vegetable!
A person in a coma is sometimes referred to, insensitively, as a 'vegetable' because they are only vegetating, and not using any higher human faculties.
By coincidence, this movie is on TV as I write, and I just heard the line.

 

[BobSmith]

I'm sick? You're cheating on a vegetable.

- source

cheating

vegetative state