WordWeb Online

1. With feet flat on the ground; not tiptoe
    
2. Unprepared and unable to react quickly
   "the new product caught their competitors flat-footed"
    
3. Having broad flat feet that usually turn outward
   "a slow flat-footed walk"
    
4. Without reservation
   "a flat-footed refusal"

See also: direct, footed, splayfoot, splayfooted, unready