Source : Webster's Revised Unabridged Dictionary (1913)

Efforce \Ef*force\, v. t. [imp. & p. p. {Efforced}; p. pr. & vb.
   n. {Efforcing}.] [OF. esforcier (F. s'efforcer to exert one's
   self), LL. exforciare; L. ex + fortis strong. See {Force}.]
   To force; to constrain; to compel to yield. [Obs.] --Spenser.