1. 
[syn: debar, forefend, forfend, obviate, deflect, avert, head off, stave off, fend off, avoid, ward off]
The Collaborative International Dictionary of English v.0.48:
Forfend \For*fend"\, v. t. [Pref. for- + fend. See Forewend.]
   To prohibit; to forbid; to avert. [Archaic]
   [1913 Webster]
         Which peril heaven forefend!             --Shak.
   [1913 Webster]
   Note: This is etymologically the preferable spelling.
         [1913 Webster]
WordNet (r) 3.0 (2006):
forfend
    v 1: prevent the occurrence of; prevent from happening; "Let's
         avoid a confrontation"; "head off a confrontation"; "avert
         a strike" [syn: debar, forefend, forfend, obviate,
         deflect, avert, head off, stave off, fend off,
         avoid, ward off]