Groovy is over, hip is square, far out is long gone. Don’t worry, though — it’s cool. “Cool” remains the gold standard of slang in the 21st century, as reliable as a blue-chip stock, surviving like ...

If it’s dipped in rose gold or is mid-century-looking, it’s probably cool. If it’s vintage but not antique—i.e., it belonged to your mom in the seventies but would look really lame on her now—it’s ...