The spear thistle, also known as the common thistle, is a prickly weed that belongs to the Asteraceae family. Due to its sharp lance-shaped leaves and spiky flower heads, it has gained several synonyms based on its appearance and characteristics. Some alternate names for spear thistle include Scottish thistle, bull thistle, wild thistle, prickly thistle, and cursed thistle. In some regions, people refer to it as the cotton thistle or the milk thistle due to the plant's white, fluffy seed heads. Despite its weedy nature, spear thistle has medicinal properties and is used in traditional medicine to treat various ailments.