Source : Webster's Revised Unabridged Dictionary (1913)

Impluvium \Im*plu"vi*um\, n. [L., fr. impluere to rain into;
   pref. im- in + pluere to rain.] (Arch.)
   In Roman dwellings, a cistern or tank, set in the atrium or
   peristyle to recieve the water from the roof, by means of the
   compluvium; generally made ornamental with flowers and works
   of art around its birm.