| adjective | causing or capable of causing death “a fatal accident” |
| adjective | of an instrument of certain death “deadly poisons” |
| adjective | extremely poisonous or injurious; producing venom “venomous snakes” |
| adjective | involving loss of divine grace or spiritual death “the seven deadly sins” |
| adjective | exceedingly harmful |
| adjective | (of a disease) having a rapid course and violent effect |
| adverb | as if dead |
| adverb | (used as intensives) extremely “she was madly in love” |
| deadliness | noun | the quality of being deadly |
| death | noun | the act of killing |
| lethality | noun | the quality of being deadly |
| venom | noun | toxin secreted by animals; secreted by certain snakes and poisonous insects (e.g., spiders and scorpions) |
| virulence | noun | extreme harmfulness (as the capacity of a microorganism to cause disease) |
| perniciousness | noun | grave harmfulness or deadliness |
| pestilence | noun | a pernicious and malign influence that is hard to get rid of |