In​ Japan, it's called kuroi kiri​ (black mist); in​ Germany, it's schmiergeld​ (grease money), whereas Mexicans refer to la mordida​ (the bite), the French say ​pot-de-vin​ (jug of​ wine), and Italians speak of the bustarella​ (little envelope). To which​ still-popular but potentially unethical business practice do these terms​ refer?