Source : Webster's Revised Unabridged Dictionary (1913)

Defective \De*fect"ive\, a. [L. defectivus: cf. F. d['e]fectif.
   See {Defect}.]
   1. Wanting in something; incomplete; lacking a part;
      deficient; imperfect; faulty; -- applied either to natural
      or moral qualities; as, a defective limb; defective
      timber; a defective copy or account; a defective
      character; defective rules.

   2. (Gram.) Lacking some of the usual forms of declension or
      conjugation; as, a defective noun or verb. --
      {De*fect"ive*ly}, adv. -- {De*fect"ive*ness}, n.

Source : WordNet®

defectively
     adv : in a defective manner; "this machine functions only
           defectively"