Dear Dr. Boli: What is the difference between a “milk shake” and a “thick shake”? —Sincerely, A Woman at the Drive-Through Window of the Burger Yurt with a Bunch of Cars Honking Behind Her.
Dear Madam: In most of the United States, a “milk shake” is a kind of semi-beverage made with milk, ice cream, and flavorings. In New England, it used to be that a “milk shake” was milk and flavorings, shaken, and if you wanted ice cream you would specify a frappe; but New England seems to have gradually conformed to the more general usage.
A “thick shake,” on the other hand, is largely made of thick, with occasional added ingredients such as brown or pink, or in extreme cases green.