I am watching a movie and this sentence is from the movie.
If you are gay, why were you so unchubby in the shower?
What does unchubby mean? since I did not find it in the dictionary.
It was news to me that this word had this slang meaning: to have an erection.
So, quite logically, "unchubby" means "without an erection".
The original sentence could be transformed into:
If you are gay, why didn't you have an erection in the shower?
A gay person might have an erection from looking at other naked males in the shower.