Poisonous/ˈpɔɪzənəs/ Definition 1 of 2Pro Tip 1/3Natural Context Used for plants and animals that naturally produce toxins. This berry is poisonous and can cause a rash if touched. Pro Tip 2/3Severity Indicates the potential danger, with death as the most severe consequence. Careful, eating even a small amount of that plant is poisonous. Pro Tip 3/3Avoidance Advice Often used to warn someone to steer clear of something dangerous. Don’t touch that frog; its skin is poisonous.