It's the knife sharpness one, they were referring to people being "sharp", which is another way of saying smart, typically the kind of person who thinks very quickly and nothing gets past them
(hope this doesn't come off as condescending, I'm including these extra details for any non native English speakers because it's kind of a slang word)
(hope this doesn't come off as condescending, I'm including these extra details for any non native English speakers because it's kind of a slang word)