Source : Webster's Revised Unabridged Dictionary (1913)

Morbific \Mor*bif"ic\, Morbifical \Mor*bif"ic*al\, a. [L. morbus
   disease + -ficare (in comp.) to make: cf. F. morbifique. See
   {-fy}.]
   Causing disease; generating a sickly state; as, a morbific
   matter.

Source : WordNet®

morbific
     adj : able to cause disease; "infective agents"; "pathogenic
           bacteria" [syn: {infective}, {pathogenic}]