Hemlock/ˈhemlɑːk/ Definition 1 of 2Pro Tip 1/3Potential Danger Hemlock is toxic and can be fatal if ingested. Recognize the risk in contexts. While hiking, they identified hemlock and avoided it. Pro Tip 2/3Historical Reference In history, hemlock was used as a method of execution, particular in ancient Greece. Socrates was sentenced to death by drinking hemlock. Pro Tip 3/3Not a Tree Despite its name, poison hemlock is a plant, not a tree. She mistakenly referred to the poison hemlock as a tree.