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.
(..) been somewhat unorthodox, but I think the end result will be a measurable enhancement - to Penny's quality of life - You've convinced me. Maybe tonight we should sneak in and shampoo her carpet. - You don't think that crosses a line? - Yes. For God's sake, do I have to hold up a sarcasm sign (..)2007 TvShow: The Big Bang Theory Title: The Big Bran Hypothesis Season: 1 Episode 2