Source : Webster's Revised Unabridged Dictionary (1913)

Seepage \Seep"age\, or Sipage \Sip"age\, n.
   Water that seeped or oozed through a porous soil. [Scot. & U.
   S.]

Seepage \Seep"age\, n.
   The act or process of seeping; percolation.

Source : WordNet®

seepage
     n : the process of seeping [syn: {ooze}, {oozing}]