Defective

1de;fec;tive pronunciation: function: adjective date: 14th century 1 a : imperfect in form or function : faulty lt;a defective pane of glassgt; b : falling below the norm in structure or in mental or physical function lt;defective eyesightgt;2 : lacking one or more of the usual forms of grammatical inflection lt;must is a defective verbgt;— de;fec;tive;ly adverb — de;fec;tive;ness noun