When a cat opens it's mouth drawing air in and up into the Jacobson's organ to process the scent more deeply than your cat's nose can. Usually resulting in an open mouth grinning expression.
"What's on this blanket? The cats got a wicked carpet grin."
"Dale, the damn cat is grinning at the carpet again!"
"Dale, the damn cat is grinning at the carpet again!"
by LordOftheTacos February 21, 2023