The Collaborative International Dictionary of English v.0.48:

Aquarium \A*qua"ri*um\, n.; pl. E. Aquariums, L. Aquaria.
   [L. See Aquarius, Ewer.]
   An artificial pond, or a globe or tank (usually with glass
   sides), in which living specimens of aquatic animals or
   plants are kept.
   [1913 Webster]