Peng is a slang word which suggests or gives hint that someone or something is attractive or 'fitting' in its purpose, The word can also be used to describe something although it has no defined descriptive properties.
"You lot are peng, thanks man" - could suggest that a friend is safe or mingles well with you
"Dem gals are peng" - could suggest that a girl/boy is sexy or quite attractive, either long term or sexual.
Used to describe anything of exceptional quality, including people Means 'fit' or 'hot' or 'good-looking'. Can also be used to describe something you like, like food, clothing, etc. Kind of like the chicken connoisseur . Originates from Nottingham, UK. Have to pronounce it in a thick British accent (not a posh one).
eg: "Mate, that chicken was real peng" or "Man, Matt's body is damn peng"