WordWeb Online

1. Infectious; having the ability to cause disease
    
2. Extremely poisonous or injurious; producing venom
   "a virulent insect bite";
   - deadly, venomous
    
3. Harsh or corrosive in tone
   - acerb, acerbic, acid, acrid, bitter, blistering, caustic, sulfurous [N. Amer], sulphurous [Brit, Cdn], vitriolic, acidulous, sulphureous [Brit]

See also: deadly, highly infective, toxic, unpleasant

Antonym: avirulent

Encyclopedia: Virulent