Source : Webster's Revised Unabridged Dictionary (1913)

Afoot \A*foot"\, adv. [Pref. a- + foot.]
   1. On foot.

            We 'll walk afoot a while.            --Shak.

   2. Fig.: In motion; in action; astir; in progress.

            The matter being afoot.               --Shak.

Source : WordNet®

afoot
     adj 1: traveling by foot; "she was afoot when I saw her this
            morning" [syn: {afoot(p)}]
     2: currently in progress; "there is mischief afoot"; "plans are
        afoot"; "preparations for the trial are underway" [syn: {afoot(p)},
         {underway}]
     adv : on foot; walking; "they went to the village afoot"; "quail
           are hunted either afoot or on horseback"