The Collaborative International Dictionary of English v.0.48:

Potion \Po"tion\, n. [L. potio, from potare to drink: cf. F.
   potion. See Poison.]
   A draught; a dose; usually, a draught or dose of a liquid
   medicine. --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Potion \Po"tion\, v. t.
   To drug. [Obs.] --Speed.
   [1913 Webster]

WordNet (r) 3.0 (2006):

potion
    n 1: a medicinal or magical or poisonous beverage