The term "poisonous plant" refers to a plant that contains chemical substances which can be harmful or even lethal to animals or humans when ingested or even when touched. There are several synonyms for the phrase "poisonous plant," such as toxic plant, venomous plant, noxious plant, lethal plant, and harmful plant. These synonyms convey the same meaning and are used interchangeably in scientific literature. Some examples of plants that fall under this category include hemlock, deadly nightshade, poison ivy, and poison oak. It is important to be aware of these synonyms as they can be useful when researching plant toxicity and their effects on health.