John Collins means in slang: John Collins can be described as a Tom Collins, except that it contains whiskey rather than gin. This is how a bartender prepares a John Collins. 1. Ice a highball glass. 2. You can also add 1 oz whiskey to your order, if you so desire. 3. You can fill the gap with either sour mixture or a suitable substitute. 4. Shake. 5. Rest of your way, you can fill with soda water. 6. Add straw. 7. Serve with cherry, flag orange, and cherry garnishes (in Slang Dictionary, added by Cali Mahoney)