“Proof” is used to measure the content of ethanol in an alcoholic beverage. The term is equal to about 1.75 times the alcohol by volume. The phrase has started to become less popular when used in conversation because of the confusion, with alcohol now just being referred to by their percent of alcohol by volume. While ethanol is 100 percent pure alcohol, it is not consumable.
The highest percent of alcohol in a consumable beverage, is Everclear and a Polish drink called Spirytus Rektyfikowany. With the high percentage of ethanol, these drinks are almost painful to drink straight and will give a severe burning sensation unless put in a mixer.