Source : Webster's Revised Unabridged Dictionary (1913)

Estop \Es*top"\, v. t. [imp. & p. p. {Estophed}; p. pr. & vb. n.
   {Estopping}.] [OF. estoper to stop, plug, close, F.
   ['e]touper, LL. stuppare to close with tow, obstruct, fr. L.
   stuppa tow, oakum, cf. Gr. ?. Cf. {Stop}.] (Law)
   To impede or bar by estoppel.

         A party will be estopped by his admissions, where his
         intent is to influence another, or derive an advantage
         to himself.                              --Abbott.

Source : WordNet®

estopping
     See {estop}