Refers to any substance that is toxic or harmful to living organisms. Used in general, scientific, and legal contexts.
The fruit of this plant contains a poisonous substance.
Please be very careful when handling poisonous substances.
毒物 is a near-synonym also meaning 'poisonous substance', but 有毒物 explicitly includes the character 有 (having), making it slightly more formal and often used in technical or legal contexts.
Compound of 有毒 (yūdoku, 'poisonous') + 物 (butsu, 'thing, substance'). The reading is straightforward on'yomi.