What it means
When you're listening to a bit of info and your inner sceptic pipes up because you know the source might be a tad spicy with the truth. It's the mental pinch of salt you sprinkle over gossip, sales talk, or that one friend who always adds a bit of their own seasoning to stories.
Usage examples
"My mate Rob reckons he saw a ghost in his shed, but I'd take that with a grain of salt — he'd had a few beers."
"The company's earnings report looks unbelievable, but I'm taking it with a grain of salt until I see the actual numbers."
"She said she got the job because of her dazzling personality, but take it with a grain of salt — her dad is the boss."
Where it comes from
Way back in ancient Rome, Pliny the Elder wrote about an antidote to poison that included a grain of salt. The idea was that a bit of salt could make something easier to swallow — literally. Over time, it wandered into English as a way of saying don't believe everything you're told without a side of caution.