poisonous

From poison +‎ -ous.

• IPA^(key): /ˈpɔɪzənəs/, /ˈpɔɪznəs/

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poisonous (comparative more poisonous, superlative most poisonous)

1. Containing sufficient poison to be dangerous to touch or ingest.
   • 2003, Charles L. Fergus, Common Edible and Poisonous Mushrooms of the Northeast, Stackpole Books (→ISBN), page 77:

     I had picked a mushroom so poisonous that particles of it, stuck to my fingers and accidentally swallowed, could have made me deathly ill, and a piece the size of my thumb could have killed me.

   Synonyms: poisoned, toxic, venomous (dialectal or archaic), attery

   Antonyms: nonpoisonous, unpoisonous

2. (figuratively) Negative, harmful.
   • 2013, Kylie Griffin, Allegiance Sworn, Penguin (→ISBN)

     He didn't want to end up like his grandfather, bitter and intractable, consumed in his hatred like an addict on haze — a poisonous attitude that would possess him all his remaining years.

   Synonym: toxic

Some speakers make a distinction between poisonous (releasing toxins when eaten), and venomous (releasing toxins (known as venom in this case) by biting a target), especially in non-colloquial speech.