Source : Webster's Revised Unabridged Dictionary (1913)

Overstock \O"ver*stock`\, n.
   Stock in excess. --Tatler.

Overstock \O`ver*stock"\, v. t. [imp. & p. p. {Overstocked}; p.
   pr. & vb. n. {Overstocking}.]
   To fill too full; to supply in excess; as, to overstock a
   market with goods, or a farm with cattle.

Source : WordNet®

overstock
     v : stock excessively [ant: {understock}]