Source : Webster's Revised Unabridged Dictionary (1913)

Needful \Need"ful\, a.
   1. Full of need; in need or want; needy; distressing.
      [Archaic] --Chaucer.

            The needful time of trouble.          --Bk. of Com.
                                                  Prayer.

   2. Necessary for supply or relief; requisite.

            All things needful for defense abound. --Dryden.
      -- {Need"ful*ly}, adv. -- {Need"ful*ness}, n.

Source : WordNet®

needfully
     adv : in an essential manner; "such expenses are necessarily
           incurred" [syn: {necessarily}] [ant: {unnecessarily}]