As a teenager she would 'sneak' out (of her house/apartment) at night to visit her boyfriend.
I'm going to 'sneak' a smoke. [=I'm going to smoke a cigarette while nobody is watching]
She took a 'sneak peek' [=a secret look] at the birthday presents hidden in the closet.
(..) - Is she? Oh. - An hour in the morning, an hour at night. Every day. Then how come an old cunt like me can still sneak up and murder you? Well, that's a different sort of fighting. Now, that's the truth, isn't it? You want to learn that sort of fighting? (..)2016 TvShow: Game of Thrones Title: No One Season: 6 Episode 8