The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

defectively
    adv 1: in a defective manner; "this machine functions only
           defectively"