Definitions of flat-footed:

• adjective:   unprepared and unable to react quickly

  Example: "The new product caught their competitors flat-footed"

• adjective:   without reservation

  Example: "A flat-footed refusal"

• adjective:   with feet flat on the ground; not tiptoe
• adjective:   having broad flat feet that usually turn outward

  Example: "A slow flat-footed walk"