IPA: /nɒnˈpɔɪzənəs/
KK: /nɑnˈpɔɪzənəs/
Not harmful or toxic to living beings.
Many plants in the garden are nonpoisonous and safe for pets.
Nonpoisonous → It is formed from "non-" (meaning not) and "poisonous" (from Latin "venenosus", meaning full of poison). The word "nonpoisonous" means not full of poison or safe from harmful substances.
Think of 'not' ('non-') being added to 'full of poison' ('venenosus') — that's why nonpoisonous means something that is safe and does not contain poison.