The Collaborative International Dictionary of English v.0.48:

Aspergill \As"per*gill\, Aspergillum \As`per*gil"lum\, n. [LL.
   aspergillum, fr. L. aspergere. See Asperse, v. t.]
   1. The brush used in the Roman Catholic church for sprinkling
      holy water on the people. [Also written aspergillus.]
      [1913 Webster]

   2. (Zool.) See Wateringpot shell.
      [1913 Webster]

WordNet (r) 3.0 (2006):

aspergill
    n 1: a short-handled device with a globe containing a sponge;
         used for sprinkling holy water [syn: aspergill,
         aspersorium]