12
evil(adjective, mean, nasty, attitude, offensive)
12
mortal(adjective, harmful, dangerous, deadly)
11
noisome(adjective, bad, taste, offensive, awful)
10
detrimental(adjective, mean, bad, nasty, offensive)
10
hurtful(adjective, bad, offensive, cruel, foul)
10
malevolent(adjective, mean, bad, evil, nasty)
10
mephitic(adjective, help, bad, evil, offensive)
10
septic(adjective, unhealthy, harmful, insalubrity)
10
toxicant(adjective, help, harmful)
9
malign(adjective, mean, bad, evil, nasty)
9
pestilent(adjective, unhealthy, harmful, deadly, fatal)
9
unwholesome(adjective, offensive, foul, disgusting, unhealthy)
8
foul(adjective, bad, taste, offensive, awful)
8
spiteful(adjective, mean, evil, nasty, attitude)
8
unhealthy(adjective, offensive, heavy, dirty, foul)
7
contagious(adjective, unhealthy, baneful, communicable)
7
pestilential(adjective, bad, foul, harmful, injurious)
7
poison(adjective, help, bad, evil, offensive)
6
damaging(adjective, bad, evil, offensive, cruel)
6
infectious(adjective, baneful)
11 years ago|15k views|share |citing 
APASmart Define. (2015). poisonous thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/poisonous/thesaurus/synonyms
ChicagoSmart Define. 2015. "poisonous thesaurus" https://smartdefine.org/poisonous/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, poisonous thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/poisonous/thesaurus/synonyms>.
MLASmart Define. "poisonous thesaurus" 19 August 2015. Web. 25 September 2026. <https://smartdefine.org/poisonous/thesaurus/synonyms>