The Collaborative International Dictionary of English v.0.48:

Stoup \Stoup\ (st[=oo]p), n. [See Stoop a vessel.]
   1. A flagon; a vessel or measure for liquids. [Scot.]
      --Jamieson.
      [1913 Webster]

   2. (Eccl.) A basin at the entrance of Roman Catholic churches
      for containing the holy water with which those who enter,
      dipping their fingers in it, cross themselves; -- called
      also holy-water stoup or holy-water font.
      [1913 Webster]