Adjective
1. causing or capable of causing death;
"a fatal accident""a deadly enemy""mortal combat""a mortal illness"2. of an instrument of certain death;
"deadly poisons""lethal weapon""a lethal injection"3. extremely poisonous or injurious; producing venom;
"venomous snakes""a virulent insect bite"4. involving loss of divine grace or spiritual death;
"the seven deadly sins"5. exceedingly harmful
6. (of a disease) having a rapid course and violent effect