The Collaborative International Dictionary of English v.0.48:

Potable \Po"ta*ble\, a. [F., fr. L. potabilis, fr. potare to
   drink; akin to Gr. po`tos a drinking, po`sis a drink, Skr.
   p[=a] to drink, OIr. ibim I drink. Cf. Poison, Bib,
   Imbibe.]
   Fit to be drunk; drinkable. "Water fresh and potable."
   --Bacon. -- n. A potable liquid; a beverage. "Useful in
   potables." --J. Philips.
   [1913 Webster]

WordNet (r) 3.0 (2006):

potable
    adj 1: suitable for drinking [syn: drinkable, potable] [ant:
           undrinkable]
    n 1: any liquid suitable for drinking; "may I take your beverage
         order?" [syn: beverage, drink, drinkable, potable]

The Devil's Dictionary (1881-1906):

POTABLE, n.  Suitable for drinking.  Water is said to be potable;
indeed, some declare it our natural beverage, although even they find
it palatable only when suffering from the recurrent disorder known as
thirst, for which it is a medicine.  Upon nothing has so great and
diligent ingenuity been brought to bear in all ages and in all
countries, except the most uncivilized, as upon the invention of
substitutes for water.  To hold that this general aversion to that
liquid has no basis in the preservative instinct of the race is to be
unscientific -- and without science we are as the snakes and toads.